Well, I have to say that the latest Windows Mobile, coupled with the iMate JasJar makes for an extremely usable PDA phone.
It seems that Microsoft has concentrated on smoothing some of the rough edges of Windows Mobile rather than adding new bells and whistles, which is just what was needed. I actually have no real complaints about the JasJar itself aside from a rather unfortunate name and a still more unfortunate carrying case. But those are both obviously minor in the grand scheme of things.
Sadly I have absolutely zero connectivity with my Macintosh - neither The Missing Sync nor PocketMac currently support Windows Mobile 2005, and Activesync 4.x under Virtual PC 7 just doesn't want to work at all. I expect that I'll have to be patient regarding the first two, and spend a whole lot of time trying to find out what's going on with the latter.
Recommended reading: Microsoft Mobile Software Still Behind, but Closing