Comcast is the worst cable provider in the history of people providing cable. The On Demand choice sucks, and nine times out of ten, it'll cut off halfway through the movie (If you can even get it loaded in the first place without getting a stupid "One Moment Please" screen for 20 minutes followed by a text saying you cant watch it, because they're having technical difficulties.) Half the time MSNBC, CNN, and USA will lag on my digital cable box worse than Crysis on my Dad's Pentium 2. The internet likes to randomly cut off from time to time. And last but not least, they charge more than any other cable company I've ever had.
Unfortunately for me, they've strong-armed the competition out in my area, so there's no alternatives, save DSL.