I have used Vonage for about 2 years now. So far they have been pretty good. My parents have been using Sunrocket and I also have some freinds that use it.. Last year was a tough one for Sunrocket.. Service stunk untill about December, since then it's been pretty good.
If I had to do it over I would probably do a BYOD (Bring your own device) and get an account with broadvoice.com . You can buy pretty much any old FXS device and configure it to work with any of the BYOD services.