I've been using this phone for over a month now and generally I am pretty happy with it. In fact it has replaced my Pocket PC for a lot of stuff, like the diary, email, and mobile browsing. Actually the browsing was a real suprise - it such a good experience now that there is a "Single Column" view for Pocket IE in 2003. This means any site is viewable on the phone, without horizontal scrolling, and that's great. Also having .net compact framework pre-installed is very encouraging. I have had a little play with creating Smartphone apps in VS 2003, and it looks promising (if a little shaky in parts). I've also used the camera much more than I anticipated...
The big downer on the phone is the battery life. If I don't charge it every night then it is dead in the morning. Some people over at http://smartphone.modaco.com/ believe this is to do with the sd card, but I have not been able to confirm this with my phone. The other big issue on the boards is that sometime the call quality can be poor (with a buzzing). Poor battery life and poor sound quality shouldn't really go to make a greate phone! But in my situation I am often at a desk with the phone on the crade (which can also charge the phone over usb, so I can easily charge my phone from my laptop), or in the car with the car charge, so it hasn't really bothered me. And I haven't really noticed the buzzing much lately.
However it's the OS that makes this phone so sweet - the great syncing with Active Sync, the great web browsing, and last but cetainly not least, the potential to write my owns .net apps.