A few weeks after signing up for the CallVantage VoIP service from AT&T, they gave me a follow-up call (which was actually a survey disguised as a follow-up call). But hey, I've got time. And I learned a few things along the way.
The surveyer told me that the major problem AT&T was having with VoIP was installation complaints. Quite simply, their typical customer could not get the darn thing to work. In some cases, the problem had nothing to do with AT&T; it may have been the result of port blocking or poor DSL throughput. But AT&T was taking all the blame for the problems.
Here is my cable modem/Wi-Fi/VoIP setup. As a geek, I enjoyed setting it up, but I can't imagine most people would have the inclination nor patience.

(By the way, how long do you think it will be before these three boxes merge into one; and whose name do you think will be on that one box? Linksys has the edge, but anything is possible still.)
Back to AT&T: the surveyer told me that they were taking a hard look at offering a paid installation service and asked me what I would pay for it. I'm cheap, so naturally I lowballed it. But I also admitted that I would bet they could comfortably charge in the $80 to $100 range because the cost of savings of VoIP could cover the installation costs in four months or less.
So, a month or so passes and here's what I see in a recent AT&T press release:
AT&T also introduced an inside wiring service designed to connect a customer's existing home telephone configuration to AT&T CallVantage Service and activate extensions throughout the home. For a fee, AT&T will dispatch a trained technician to the customer's home. The technician will reconfigure existing lines and telephone jacks, install additional jacks if required, and provide limited assistance with service set-up. The interval for scheduling service is two to five days.
This is great news. Of course, the devil is in the details. Assuming AT&T handles installation like your typical cable company, they could do more harm than good to their business, but I'll assume the latter. Installation is going to be necessary for the vast majority of potential VoIP users and this could provide a nice advantage for CallVantage.
But installation is also going to slow down this revolution, at least until these many technical and operational quirks are resolved.