We are starting to sell Broadvox via the Samsung Officeserv systems.
It seems the weak link is faxing. Faxing doesn't seem to be as solid with SIP as it should be. We have our office faxing forwarded off to Myfax and that does the job.
In the Pacific NW, Comcast is getting better and better at providing solid and very fast internet. Whether the customer uses Comcast or DSL we can always have the fax handled on THEIR side if possible.
We are agents for various companies selling split service T-1s, dynamic T-1s, etc. Most of these companies want 3-year agreements. The problem is that the bandwidth will be ridiculously low (comparative to cable, etc) in less than a year. Cable will be 75x faster for a lot less money than any T-1 service, even bonded. A year from now someone with 768k internet might as well be carrying a club over their shoulder.
That is where we see SIP having a niche. Super-fast broadband and then SIP trunks vs dead-slow dinosaur internet. Mr. Customer would you like SIP and 50mps download speeds for 60% the cost of a dynamic T-1 and maybe 1.5mb speed?
I know the old argument that nothing is more reliable than a T-1 and although that might be true, there was once nothing more reliable than a modem providing 1200 baud service. T-1s are coming to an end.
We still do have customers that insist that ultimate reliability is the bottom line, so T-1s are still in the game for now.
We are also getting our toes wet with dual-wan routers that allow cable on one wan and failover to DSL, or other alternatives to try and beef up the reliability of non-T-1 connections.