How do you find the HD picture quality?
As a confirmed pixel peeper and recent DirecTV customer (switched at the end of April) I feel qualified to answer this question.
On some channels, Dish HD is almost as good as DirecTV's HD. There is a slight loss of picture detail, and some evidence of color quashing. On others, particularly on Fox Sports Net, the picture quality on Dish is greatly inferior. I would describe the differences as mostly subtle, with the exception of FSN. The average person is probably not going to notice the difference.
What made it worth switching for me is that Dish has some channels that I watch quite a bit in HD that DirecTV does not have (BBC America comes to mind) and DirecTV's SD quality makes a worn-out VHS tape look good. By comparison, Dish's SD quality is quite good, better than VHS but worse than DVD by a wide margin. The similarly-priced package I switched to included several movie channels that I am likely to watch, which replaced channels I never watched on DirecTV. There are a few odd channels that are not in HD - Disney, ABC Family and ESPN News, for instance. And Dish appears to be saying goodbye to AMC, which doesn't matter a bit to me, but I know it will to others.
The other factor was that I had one of the slowest DVRs on the planet from DirecTV. It was awful, and created all sorts of problems for me. The Hopper works the way a DVR should - fast and responsive, even while recording 3 things at once. I understand that the problems with the DirecTV DVR's was not universal, and while I was assured DirecTV was aware of and working on the problem, I figured giving them over two years to fix it was enough to convince me that they'd probably never get it right.