^^^ THIS!
XFINITY Customer right now, and would love to just go with the next level of Internet with them and nothing else. HD Antenna for local stuff, Hulu Plus, HBO, and that's it. If Apple TV has other things to offer without the hands of XFINITY I'd be all over it.
I am also at the mercy of Comcast, but last April cut down to the exact scenario you described. We bought a $50 outdoor antenna and got Internet Plus, which gives us 50Mbps down and 12 Mbps up, along with HBO Go, for $70. Factor in Hulu, and the fact that we own our modem, and we are paying less than half for roughly the same services we used with cable.