I switched from DirecTV to Dish and I regret that decision because immediately I was dissatified with their picture quality. During the time with DirecTV, I also had their combined Tivo receiver and I liked it better than Dish's DVR.
On the up side, to get my local channels with Dish, we only need one dish whereas with DirecTV, we would need two. However, I *believe* this depends on your area. Perhaps, you wouldn't need two dishes (unless you are adding HD?). Also, Dish offered us a receiver with a dual tuner which meant we could watch and record different shows on two tvs without paying the cost of an extra receiver. DirecTV didn't have such a receiver at the time I switched, but now I think they do.
Service wise, I've found both DirecTV and Dish to be about the same. As far as deals go for existing customers, my brother upgraded to HD for free (no equipment costs) with DirecTV, but he had to make a commitment that he couldn't cancel his service for a year. Since he had no plans of switching, it was not a big deal. They may have made an exception for him though. I'm not sure if that is the norm.
