I had several questions prior to signing up for the service all of which were quickly answered by customer service (via e-mail).
The adapter arrived the day after I signed up.
It worked worked out of the box - in front of my firewall, behind my firewall, with NAT, and without NAT.
The documentation, although slim, covered all the required information and some that I did not expect to see ( Linux iptables information for example ).
I substituted the VoicePulse service as the default outgoing line and no one has noticed the difference. One call did have an echo, but it is not clear what caused it; there was no echo on a followup call.
I have not used 911 on my land line and do not see it as a major issue. I just made the local Public Safety number one of the speed dial numbers (same as I did on the cell phones).
I pluged the adapter into the same UPS that protects the DSL router.
Overall, I am very impressed with the service and would not hesitate to recomend it.