I've had it through Time Warner (the cable provider in my area) for the last 3 or 4 years and I'll be ordering it again sometime this week.
Most of the games are broadcast in HD, but not all. It depends on the feed of the particular broadcast you are watching and has nothing to do with Comcast or any other provider. It's based solely on the broadcast over which you have no control.
Sometimes you get the home team's broadcast and other times you get the visiting team's broadcast. Again, you have no choice although every now and then both broadcasts will be available on different channels.
Go Indians!