I have a T-Mobile SDA-II. When I first got it I used ActiveSync 4.1 and found contacts at random would be deleted from Outlook / the phone. The fix for this is to revert to ActiveSync 3.8. The problem I've now got is I can't sync MP3s using Media Player and even copying them over using drag and drop in explorer is less than reliable. (It'll get half way through copying a file then fail.)
I am wondering if upgrading to activesync 4.2 would solve the problem and leave my contacts unmolested! :-) Is anyone else successfully using Outlook 2003 / T-mobile SDA II (or C550 I guess) / Activesync 4.2?