Dan,
we have nothing but good feedback from this customer so far, only 1 of the 40 sites has an inferior connection ( ISDN 128K ) and this is almost inadequate because as soon as anyone uses the net, it degrades the voice quality.
I have used the boxes on dial-up but the only thing was that if you didn’t connect at more than 33600 then you had delay and echo due to modem compression. The way I did it was I turned my laptop into a proxy server and did all of the required port forwarding and everything works. I can give you more detalils if you wish..
Have you done much work with the units using the telnet prompts? I have manuals and a few neat tricks too! I have yet to find a unit that has better voice quality than the QTelNet products. I am doing some testing with the ericsson webswitch 100 ( 4 port FXS running the same VxWorks NMM software through telnet and they are 100% compatible with QTelNet, you just have to do the bulk of the config through the telnet)