instead of constantly bringing up theories in threads about how you want to know if you should do this or that, why not just try it out? borrow a POS phone, or dig an old one out of a draw or something, take your iphone sim, place it in the POS phone and use that for texts/calls and use you iphone for ipod/apps and see how long you last before you switch the sim back again.
seriously, the fact i can check my fav websites while i'm bored rather than waiting until i get in is a good thing for me. lets me do other things during that "sit at the pc and browse the internet" time. i'd much rather do that crap while i'm sat around waiting for something or got nothing better to do.
and for me 2 devices is a pain. i got a 1st gen touch and had a little SE phone purely for texting. when 2.0 came out and i got email etc on the ipod i decided "screw this" and got the iphone. email, internet, music, apps and phone anywhere, any time, and one less thing bulking up pockets. i don't why anyone would want to take a step backwards, but if it's what you think you want just try it instead of arguing with yourself and people on this forum. theories look great on paper but aren't always so good when put to practice.