March 2010-Present.
I switched because I was frustrated with the HD offering from Comcast, or lack therefore. Before that, I had been with Comcast or another cable company (AT&T, TCI, Viacom, etc.) my whole life.
Also, 722, while it is dated now, it was a better (and cheaper) DVR than whatever Comcast was using, at the time.
Since then, I've shaved the cord, but I remain with Dish, because of cheaper pricing, more HD, BB@Home, and the Hopper.
I did experiment for a bit with cutting the cord about a year ago, but between data caps, and hoops I had to jump through in order to watch some programming, among other things, for me, it was not worth it, and that was when I upgraded from the 722 to the Hopper.