I am running the 9530 on T-Mobile USA with no issues for the EDGE. One hint, once you get on the voice network, call customer service. Ask for the Unsupported Device department. They got me all setup, and my storm has run for 2 weeks in a way that it would if I bought the Storm from the T-Mobile store. I love my 9530, but either way, you'll love the Storm over all the lame offerings that T-Mobile offers now.
Th1nm1nt...The World's Greatest!
Currently: Blackberry Storm 9530 on T-Mobile US Network
Previously: HTC Touch Pro, HTC Wing, HTC MDA, and HP H6315