I never thought I'd forgive Time Warner for abominable service before I switched to FiOS—but I just might, if their plan to lease their pipes to AT&T and Verizon makes using an iPhone in NY actually tolerable. UPDATED.
AT&T's iPhone problems are two-fold. There's the wireless aspect, which is having enough towers with enough spectrum for everybody—that's probably what you're familiar with. (The problem in really crowded areas is that there's only so much wireless coverage you can provide before you run into issues like cross talk. We'll see how it goes down at SXSW this year, since AT&T's almost certainly loaded Austin after last year's implosion. In the meantime, the FCC is pushing to get more spectrum into carriers' hands to ease congestion.)
The other side is backhaul—the actual pipes carrying data. I've never been able to get AT&T to tell me how much of their backhaul is copper vs. fiber, which would tell us a lot about their backhaul capacity. (Fiber can carry a lot more data to and from towers than copper, obvs.) Supposedly, they're increasing fiber deployments alongside with their U-Verse rollouts, but I'm not sure how (or if) that's been affected by the slowdowns in U-Verse deployment. (Presumably not much, if at all.) Either way, their needs for backhaul have been exploding.