I'm working on an article on Exchange ActiveSync for the magazine. Unfortunately, I don't have it working for my device yet-- John's iPaq 6315 works on 3sharp's server, but something is funny with my server here at home, and I'm going to be troubleshooting it this week. A couple of resources that look useful: this extremely detailed TechNet webcast and Chris De Herrera's troubleshooting guide (which mostly covers "regular" ActiveSync) on CEWindows.net.