Speaking personally, even if the networks were flawless (and we all know they are far from that), I'm not interested in paying $100/month, on top of my home broadband (which gets far more use than anything I would ever use w/ a phone). The $50/month for my basic cell phone service is more than enough money out of my pocket.
Side note; I might be alone on this, but I want a cell phone that's just a phone. I'm not interested in a built-in MP3, a camera, video, or whatever else the companies are trying to sell. My favorite phone way back when was the old Motorola flip-phone, mainly because in addition to being just a phone (and an easy to operate one), it was rugged as hell (dropped on concrete several times and not a scratch or failure to operate). Today's phones (currently use a base-model Nokia) feel fragile as hell and I doubt could take the punishment. I'm also not a fan of touch-screens (easily scratched, dirtied, etc), so even if the iPhone wasn't so overpriced (it is), I still wouldn't buy it.