I've jailbroken and unlocked my Iphone 3S and am currently with T-mobile on a month-to-month plan (also use it in Guatemala with Tigo). I was thinking of getting an Iphone 4, unlocking it and using it with T-mobile and of course, putting a local sim card in it where ever I am.

I see a lot of EVO's on Ebay for a good price. Any problems with purchasing one and using it worldwide on any network?