Bottom line: the Treo 650 is a superb device for Palm OS users, period. However, since it's currently only available on Sprint, I'm holding off.

PalmOne has been working on the Treo line for a while. Their Treo 600 is arguably the most popular PalmOS-based smartphone, and the Treo 650 is evidently an attempt to improve on its strengths by adding features.

First, the gross physical attributes. The Treo 650 is about the same height as the SMT5600, but it's much wider and somewhat heavier (although lighter than the 7135). The screen is large, very bright, and very sharp-- the only better screen I've seen on a handheld is on the iPaq 6315. It's physically smaller than, but as bright and clear as, the excellent screen on the Tungsten series; the screen is clearly visible outdoors and in sunlight. Below the screen are the familiar four Palm application buttons and a five-way nav device, plus "home" and "menu" buttons; below the buttons is the Treo's QWERTY keyboard (more on that in a minute).

Phone: the Treo 650 worked flawlessly as a cellphone. I was easily able to make and receive calls, and the integration between the built-in address book and the Phone applet is excellent. I had a little trouble using the keyboard to dial, just because the number keys are much smaller than the ones on the SMT5600 or 7135. For the first time, I actually found myself waiting to make phone calls in the car until I could pull over or stop and actually see what I was dialing! Speaker and speakerphone volume were both quite good. There have been reports on Slashdot, and elsewhere, of poor audio and voice quality on the Treo 650 but I didn't have that problem at any time during my tests.

Messaging: PalmOne includes two messaging apps: one for SMS messages and VersaMail for email. I was most interested in Exchange ActiveSync, so I spent a good bit of time with VersaMail. Overall, I found it inferior to Pocket Outlook in both ease of use and stability, although VersaMail does a better job of handling multiple email accounts and letting you quickly switch between them. When you configure a mail account with EAS (you can only have one at a time), the device warns you that it's going to erase all of your stored messages and calendar data, then resync. I lost my calendar data by accepting this warning, then forgetting to configure my desktop conduit to skip calendar sync-- be careful! (To be fair, this was entirely my fault, not the Treo's.) Once set up, Exchange ActiveSync worked fine, although there are no sync logs kept on the device. This would be a helpful troubleshooting feature, and I hope Palm will add it in th next release (along with sync for contacts and additional mailbox folders).

Synchronization: I had a few minor problems with ActiveSync on the desktop, but those were easy to resolve. Over-the-air sync with EAS worked well, and I like the ability to choose what gets synced over the air and what gets synced over the wire-- the Treo 650 forces you to sync mail and calendar data or nothing at all. I also tried using PocketMac Phone Edition to sync the 5600 to my Mac OS X desktop running Entourage. BIG mistake. PocketMac is unstable and buggy; their technical support is slow (when they respond at all), and the software doesn't do what it claims. Avoid.

Bluetooth: I tried to use a Jabra FreeSpeak 250 headset with this phone. The headset is listed as compatible with the Treo 650 as a headset device. This is odd, since it worked fine with the SMT5600 as a handsfree device. One annoyance that the manual didn't mention is that with a headset-only device, you have to push the headset button to transfer a call from the handset to the headset-- this contradicts the manual's assurance that when you have an active headset, calls are automatically routed to it. Fortunately, PalmOne has a KB article that explains how this really works.

Other: the Treo 650 has an integrated camera that is reputed to be quite good. My device was a preproduction test unit and didn't have a camera, so I can't say whether it's any good or not (but these side-by-side comparisons make the Treo 650 look pretty good). Battery life has been excellent, and the addition of a replaceable battery is quite welcome. The internal speaker sounds great when you play MP3s through it, which surprised me a little bit. The addition of a sliding "mute" switch on top of the phone was a very useful touch; it's trivial to make sure the phone is muted before you walk into an important meeting, or church, or wherever.

Bugs and annoyances: most of the annoyances I had with the Treo 650 centered around Sprint's service in my area; I had trouble making and receiving calls in and around my house, and for a whole day I couldn't get my voicemail. This is not to say that Verizon or T-Mobile has great coverage in my neighborhood either. I had a little trouble getting used to the keyboard, which is awfully small. I already mentioned its effect on dialing; another minor niggle was that I never did figure out how to use keyboard shortcuts for menu commands. However, with a keyboard-aware app like DateBk5, it's possible to work without using the stylus at all-- an impressive accomplishment.

In all, this is a terrific device, although at $369 for new subscribers it's fairly expensive (although, interestingly, cheaper than the Kyocera 7135 from Verizon!) I'm waiting for either a GSM or Verizon version before I take the plunge, but the screen quality, speed, and utility of the 650 make this a very strong contender as my next device.

Bottom line: the SMT5600 is a great device, but it's not exactly a replacement for a full-function PDA, so I'm sending it back.

There are already lots of reviews of what the phone looks like and how it works, so this won't necessarily be a complete review of every aspect of the SMT5600. Instead, it'll hit what I think are the high and low points. Microsoft has been positioning Windows Mobile smartphones as "phone-plus" devices that combine solid phone functionality with mobile messaging and the ability to run various applications (both productivity apps like Outlook and line-of-business applications).

First, the gross physical attributes. The case feels solid, with no flex. The phone is relatively small and light (I'll post a picture of it next to the Treo 650 and my trusty Kyocera 7135), and it fits comfortably in a shirt or trousers pocket. One of the first things people say when they see the 5600 for the first time is "wow, what a great screen!" The screen is large, clear, and very sharp. The keypad has a nice crisp feel. I never really got used to the 5-way rocker pad; I found it too easy to accidentally press it to the left when I was trying to click it down.

Phone: the SMT5600 worked very well as a phone. Audio was clear and crisp, and the speakerphone had adequate volume for use around my (noisy, child-filled) house. Address book/phone integration is good; the 5600 includes a Photo Contacts app that lets you take or import pictures and add them to the contact so they'll be displayed for incoming calls. This was a nice touch. One useful feature: as you dial, the phone app will display contacts whose phone numbers match what you're typing-- if you type "800 325" it'll jump to the first contact with those numbers (in my case, Delta Airlines). While you're in a call, you can easily switch to other apps, and there are dedicated buttons for viewing your calendar or the contact data for the person you're talking to.

Windows Mobile: this was my first real experience with a Windows Mobile device. I was very impressed; it was stable and easy to use (not to mention being very familiar-looking). The bundled applications all worked well, and I found Windows Media 10 Mobile Edition to be a very nice addition. If I didn't already use an iPod, this would be a neat way to listen to music, and with WMP10 on the desktop you can transcode video to watch on the phone. This is a great app for commuters and others who have disposable time to watch mobile video.

Messaging: what can I say? I had no trouble using OMA or Exchange ActiveSync with this phone, and this was one of its best features. When Always-Up-To-Date is properly configured, you have essentially always-on email in what looks like an ordinary cell phone. The included MSN Messenger client was also very useful, although pecking in a complex Passport password on the keypad gets old pretty fast. In fact, I quickly found that the utility of always having my mail was diminished by having to use a 0-9 keypad to answer it. The SMT5600 includes the Tegic T9 text input system, which worked pretty well, but it's no substitute for either a QWERTY keyboard or pen text input.

Synchronization: I had a few minor problems with ActiveSync on the desktop, but those were easy to resolve. Over-the-air sync with EAS worked well, and I like the ability to choose what gets synced over the air and what gets synced over the wire-- the Treo 650 forces you to sync mail and calendar data or nothing at all. I also tried using PocketMac Phone Edition to sync the 5600 to my Mac OS X desktop running Entourage. BIG mistake. PocketMac is unstable and buggy; their technical support is slow (when they respond at all), and the software doesn't do what it claims. Avoid.

Bluetooth: I used a Jabra FreeSpeak 250 headset, which I quickly grew to love. The SMT5600 paired with it immediately, and I could initiate and answer calls with it (although I never got voice tag recording to work properly). I didn't test using the phone as a laptop modem via Bluetooth, nor did I test other Bluetooth devices like the Pharos GPS module that i use with Streets and Trips. (I did put Pocket Streets and Trips on it-- pretty darn cool!)

Other: the included camera is nothing to write home about; it does a serviceable job, and the included camcorder app works well enough for casual use. Battery life has been excellent, although I haven't spent that much time talking on it.

Bugs and annoyances: sure, there were a few, but nothing major. Frequently, the SMT5600 would decide that an appointment was an all-day event, so it would start alarming me at 0830. If you use the keylock function (which you really need, since this isn't a clamshell phone), you can't answer or make calls with a Bluetooth headset. For some reason, the phone wouldn't auto-set the time from the AT&T network. The phone app doesn't like dialing numbers with slashes (425/818-0484 would only dial "425"), so I had to go through and reformat most of my phone numbers. These are all minor problems, though; overall, the device was as stable and reliable as other phone-only devices I've used.

One odd note: several other people I know who have the SMT5600 complained about radio interference. My old Motorola GSM phone would buzz my desktop speakers whenever it communicated with the cell, and its successor did the same thing in the car. However, the SMT5600 sits right between my desktop speakers and hasn't generated a grain of noise since I got it, and it's been silent in the car, too. Maybe I got a newer rev or something. (The 650, OTOH, buzzes the baby monitor all the time-- I can always predict incoming calls!)

In all, this is a very impressive device that delivers on its promises of high functionality in a small package. You can only get it for AT&T's network in the US, although if you unlock it it will work fine on T-Mobile. Cingular doesn't sell the phone in its retail stores, but Amazon still has it for a net price of $-25 for new subscribers.

Update: added some notes on the SMT5600's phone functionality that I forgot in the first draft.