Today is a very happy day for all you T-Mobile G2 users out there, the company is now pushing out the 2.1 ROM update to handsets as an OTA (Over the Air) download.
If you have not had the update yet check under settings if you can search for it as you should pick it up that way.
All user data will be wiped so please make sure you backup before you update but now thankfully at long last G2 owners get the new marketplace, being able to use Live Wallpapers and Google Navigation
Link: T-Mobile UK Forum