Follow-on from my AT&T Uverse "upgrade" to Uverse Voice:

Everything is now working fine. I have no idea why YouTube was acting wonky on my desktop, but rebooting it (which I had to do anyway, for a software upgrade) totally fixed the problem. I wouldn't be surprised if the new VDSL box was "learning" about my connection for the first day and was adjusting its buffering or whatever. (Or, that my computer had some learned model of buffering quick-start parameters which was suddenly all very, very wrong.)

Supposedly I get free voicemail as part of the deal, but at least for now I'm continuing to use my plain old home answering machine. Whatever benefit I'd get from worldwide access to my voicemail would be immediately lost by having to deal with the horror that is the AT&T app. These ratings tell a sad tale.