I can add a few data points to the drop out problem.
I started using Uverse (VIP 1225) with a Pioneer Elite receiver and had no problems whatsover. I was running all HDMI.
Then, I "upgraded" to an Onkyo 3000--the audio drop-outs started immediately. Interestingly, though, the audio was fine for Dolby Digital broadcasts, but was unbearable for non-DD. During a program, the Onkyo would audibly click every few seconds, like it was switching formats or something. The Pioneer receiver never did this. In fact, I still am using the Pioneer receiver for my second TV, for a true apples to apples comparison, and there are no drop outs.
Also, as noted by others, the problem is "fixed" if you go into the audio menu of the Uverse box, and switch the digital audio out from "surround" to "stereo." Of course, when you do this, you lose surround sound (including the true Dolby Digital broadcasts), which kind of defeats the purpose of having a quality system.
My conclusion: Uverse has a problem with the audio stream, in "surround" mode, for non-Dolby Digital broadcasts. Something about the audio stream is interrupted. Some receivers, like Pioneer, can handle these little interruptions seamlessly for no audible drop-outs. Other receivers, like Onkyo (or Integra), have a terrible time with these interruptions, which result in constant dropouts. I even put the Onkyo in "Pure Direct" mode (i.e., bypassing all video and audio processing), but it didn't help.
I showed my tech this problem, and of course he blamed the Onkyo receiver. Also, if you connect the Uverse box straight to the TV (via HDMI), there are no dropouts.