im currently using tmobile uk. their fair usage of 'unlimited internet' is 1gb, which i think i quite reasonable, considering that i use 3g connection 24/7 cuz i have no wifi at home, and i've never been charged anything extra.

having said that, i dont think the coverage of tmobile uk is all that great, i get full 3g signal when i put the n900 near the window, but when using in the middle of the house, 3g signal is non existence. and yea most importantly, the internet speed isnt the fastest, i compared mine with a friend using iphone 3gs on orange, and a friend using Nokia E71 on vodafone, and im the slowest.