According to the press release, T-Mobile's UMTS/HSDPA service can surf at a speed of up to 1 Mbps, and a complete list of the 3G markets can be found at http://www.t-mobile.com/coverage
In what is most likely preparation for the launch of the G1, T-Mobile on Friday announced the launch of new 3G markets. According to the press release, Sacramento, California launched last week, and Memphis, Tennessee and Tampa, Florida will be blanketed in 3G goodness this week. Additionally, Washington, D.C. will launch by late November, bringing the service to 120 major US cities by the end of the year. In a statement, the senior vice president of Engineering and Operations, said that the 3G expansion will continue.