I signed up, got my gizmo & phones and I have to say it works great! In fact, I'm canceling my local phone service entirely, so $16.58/month wil be it. In case of outtages, just get a backup dialpad.com (or similar) prepaid card for emergency use so you can still call over the Internet.
Also, hooking it up as they show results in a slowdown of your Internet connection. Just get any broadband router, hook your modem up to it & then run separate cables from your router to the computer & to the gizmo. I have 90% QOS without doing any tweaks.