Less than a week ago I signed up for a trial of AT&T's new CallVantage service.
Based on some initial calling I can only say that people on the other end have no clue I'm using VoIP until I tell them so. The call quality is as close to PSTN as I have heard to date. The set up was easy as easy can be, and most of all, it all worked as promised. There was no jitter, latency, rebuffering or packet loss that I could detect.
Candidly, I'm not surprised the service is this good. AT&T has too much to lose in putting out an inferior product. By putting out a product that is at basic mode already better than the competition which went first, AT&T has really fired a shot that will be heard around the telephony world.