Well, that is not good.  I am in the process of determine if I want to switch over and have witnessed the pixelation problem first hand on a friends TV. I couldn't not live with periodic pixelation. I have a Pioneer Plasma for a reason.

If you google u-verse pixilation, you will find tons of people discussing this issue.

If I were you, the first thing I would do is get a handle on your packet statistics. Find out how to determine errors and other issues.  Once you have this knowledge, you can determine if your tech is improving the situation when he comes out.

Here is an example post of what I'm referring to

http://www.dslreports.com/forum/r20599613-Pixelation-in-UVerse-TV