I'd previously written about MS' support position on VERITAS Storage Foundation for Exchange. Sometime between then and now, MS released a KB article (895847) that sets out their support policy for hardware and software replication solutions. It outlines support boundaries for three important categories: asynchronous software replication, synchronous hardware replication in a geographically dispersed cluster, and sync hardware replication not in a dispersed cluster. Well worth a read if you're interested in this category of products.