The Xperia Ray will only work on T-Mobile USA's 2G network. I too want this phone so bad but I do not want to pay through the nose tied to AT&T's contract. I've been trying to find out if it will work on T-Mobile's 3G network.
The Ray works on UK's T-Mobile (and i'm sure in other countries) and they have the i version. I looked at the specs that's being sold on Amazon and it does not say 1700Mhz so I came to a conclusion that it's pointless to get it if I can't use 3G on it. So now i'm shopping around for 2nd best
(the Arc is too big for me).
For about $30 a month you can get this FREE in UK on a 24 month contract with 500mb-1GB data, 300-500 minutes, and 300-unlimited text! That's damn cheap! We are really getting ripped off here in the US!
It will cost me over $300 to buy it and then $75/mo on AT&T for a 2yr contract with only 200mb of data! That doesn't make sense, might as well get the iPhone 4S for $200