I finally got Comcast out to install the X1 as part of my double play package (dropped the telephone). The X1 is apparently in high demand. I can confirm it is a significant jump in picture quality over my Dish HD DVR. In addition to the better pq, it is an impressive box with a lot of features (search, on demand, HD priority, recording options, etc.) I've just played with it for 1 day, but really like what I've experienced so far. I have no regrets making the swap from Dish so far.
Kenreau
I really don't know. Nothing else changed on my end. Direct box swap and that was it. I'm guessing higher quality hardware inside the box. The difference in video quality between X1 and my Tivo box is even greater.