Will make calls but wont do SMS or mobile internet for me today. : /
From my experience T-Mobile aren't great, at least in the South East
Yep - I can confirm this as well, in peak times (weekday evenings and weekend afternoons and evenings) my n900 cant even connect to load any web page. It reports a 3.5G connection, but every web page just times out

Central london is OK, but when i get home, no web, every day. Outside peak times, it is ok...
Most used apps since I got the phone end of Nov
the console - ssh to my jumpbox and then I can connet to all my switches, for me, on a phone, that is just so cool
The multi tasking - it works so well
pixelpipe - makes it so easy to post anything online
conversations widget - brilliant integration along with hermes which made things so simple
ecoach - record my bike journey to work
RSS reader - no expanation needed
PDF reader - handy for all my datasheets
the micro-b browser, best mobile browser I have ever seen
gpodder - great for podcasts - love the online sync
wireshark - cos its cool and my job
suprise app - fbreader - I read an 800 page book using this, my first ever e-book, and didn't find it annoying and didn't really miss having the paper version, which was a suprise. The screen size was fine as well..
All in all, this is the best phone I have ever owned