The 750 and W800 are gsm units and will be used on Cingular and T Moble networks to start off. Both are the new 2 MP camera phones, that are almost identical inside. I can't wait. Friday the 26th the phones will be available on the sony E=shop site.
currently no US carriers have the w800i or k750i. but you can always just buy a phone from overseas or from ebay, have it unlocked and unbranded and then use it with any carrier you want!