I think what I'll do is pick up a SIM and try it out. After a month, then I can decide if I want to port the number. Best part, I can toss the SIM in the iPad for data and do side by side comparisons with AT&T.

Not sure why I didn't just think of this earlier. This is the problem with the contract subsidy market, it changes your thinking to assume locks are present everywhere in the mobile market.