Isn't the only iPhone that is compatible with HSPA+ the latest iPhone 4S? If so, then how aggressive can T-Mobile really get for contract lapsed AT&T customers, when iPhone 4S users will presumably be locked in for another year and a half?
Good question, smart customers know that breaking a contract and paying termination fee during the first 6 month of a contract is a win, breaking a contract within the 6 - 18 months period is a breakeven, and -get this- the last 6 months of your contract you actually already paid for it, and AT&T continue to force you to pay around $20 in subsidy. That's why I laugh at people who say "oh I am going to stick to my phone one more year". You are giving their greedy CEO nothing but additional pure profit.
Think about the selected few who were wise enough to sell their iPhone 4 and get an iPhone 4S a year or so after their contact.