Not any network, any compatible network. It's a GSM phone, ATT and TMobile I believe are the only GSM networks in the US. Verizon, and Sprint use CDMA. Different technology. ATT exclusive contract with Apple ends next year, hopefully then we see it go to other networks. Which is one reason ATT is locking you into a contract that extends past their exclusivity agreement. Funny how they didn't make you sign a 2yr contract while their were the only ones that had the phone, and got people to pay full price for it. Now that that's not an option any, ATT is subsiding the phone and getting people to agree to a two year contract. Very clever, getting three years out of two!

Last I heard that ATT's 3G network was much behind the buildout of Verizon's and Sprint's EVDO networks (and EVDO-A which is even faster), but that my be just company propaganda don't know for sure.