I don’t think I would have canceled cable if I hadn’t basically been forced to. I’m still using MythTV as my DVR, and it works well — when it can capture video. Two years ago I was capturing HDTV using the little-known firewire output on our HD cable box. Then RCN turn encryption on all the channels, and I had to go back to analog SD cable capture. Early this year, Comcast announced that they’d be turning off the analog channels, except for the most basic broadcast stations. That meant cable would become almost completely useless to us, my MythTV can only record analog SD and we never watch live TV.
Since most of the shows we watch are either a) available over the air, b) available legally online, or c) available other ways ((like watching the red sox at a friends house, is what I’m referring to here!)), we couldn’t see the point of spending 40$/mo on top of our internet connection cost for TV.
I bought a 30$ powered antenna at Target, a 100$ HD capture card for my mythtv, and we’re now back to recording and playing back HDTV.