New York, NY: At IPTComm 2007 at Columbia University, Brian Whitton spoke about the network. He disagreed with Jeff Pulver's assertion that innovation wasn't happening because people didn't have guts. Whitton showed slides of Verizon's Fiber-to-the-home network that uses Voice over ATM, and showed the new architecture where SIP FTTX NIDs (ATAs) that talk to BroadWorks. The new architecture also included the Nortel CS2K (likely for PSTN access from BroadWorks).
He said the innovation is stymied by the diversity of vendors; there's no one source for all of the devices, and they don't all interoperate very well. It's a lot of work to integrate all the pieces. He also pointed out that there are more independent pieces (servers, routers, SBCs, call control servers, etc.) than in the traditional PSTN, not fewer.
So the complexity of integration seems to be the largest difficulty.