Eight months ago I moved and left Dish for Comcast. I can not speak highly enough of their Internet service and from my experience their overall customer service. I however have little to say positive in regards to the Television service. In the Detroit area the picture on HD is very comparable to what I was used to with Dish. Even though I was not thrilled with the picture on SD with Dish, Comcast is terrible. I ended up splitting the signal to by pass the 3412 DVR and when watching SD have to switch to another Input, still the though the picture is bad.
I have little good to say about their DVR's. I have had a 6412 and now the 3412, both are terrible. They are so unresponsive it is virtually impossible to channel surf. There is no way to program favorites where you can surf them forward and backwards. The guide therefore has everything listed with no way to pare it down. When trying to go fast forward while watching recorded programs you may go fast or not, as the recorder does not communicate well with the remote. When trying to press numbers to go to a channel directly it might go there or may not. It is a extremely frustrating to operate.
For these reasons I have decided to go back to Dish. And oh, did I mention HD? As Someone else suggested Comcast require no contract and there is no start-up fee for the DVR, so try it and see if you like it. Your milage may vary.