I switched to U-verse about 1 year ago. Overall I am very pleased. The picture quality blows away Comcast and other cable companies, and is about the same as satellite providers (but without the weather interruptions). On Demand content falls behind Comcast for the network and cable channels; you don't find very many full seasons available, just a handful of shows for each program. The On Demand content for premium channels is the same as Comcast as far as I can tell.
I have two basic gripes with U-verse. The first is the way they have set up the multiple tuners. With Comcast, I had a DVR box with dual tuners and the tuners were always active, recording up to 1 hour of whatever channel they were set to. So, if you were watching two football games at once, you could pause one, switch to the other tuner to watch the second game for a little while, pause the second game, then switch back to the first game and pick up where you paused. Rinse and repeat. Very handy.
With U-verse, that feature is not available. Although you have 4 tuners, if you are not watching them then they are not on, and you cannot pause or rewind to any of the content. So, if you are watching one game and then switch to another game, you will be picking up the second game as though you had just turned on the TV, and then if you switch back to the first game you will have missed all the stuff that went on while you switched. The only "fix" is to set up a second receiver in your house to watch the second game you want to see. That turns on a second tuner that starts saving up to 1 hour of content for live viewing. The only catch is, you cannot pause to switch between tuners. If you switch over to the second game, the action will be live.....you can rewind back to the point that you last saw the game, but you cannot pause, switch tuners, and then pick up the game where you left off. I am working on a fix for this by connecting a second receiver to my TV so that I will actually switch between TV inputs, but the remote works for both receivers so that will be tricky.
Also, I think the U-verse user interface is much worse than Comcast's. Comcast's UI was developed by TiVo, so you kind of expect it to be really user friendly. The U-verse search feature sucks, and the series record settings can get screwed up at times and either miss shows, or not record the entire program. The skip forward feature only moves the program ahead 14 seconds, so its pretty useless (I just use fast forward and try to push "play" at the right time). A couple other buggy issues with it that I can't think of right now...
Overall I prefer U-verse because picture quality is very important to me. I have never had any service or outage issues. I did sign a two year contract in order to get a substantial bundling discount, so we'll find out next year how bad they try to gouge us on pricing