I wanted to share my positive experience with Phone Power as well. In short, I had some problems initially (all likely self-inflicted) but once those were resolved it's been smooth sailing so far. Call quality has been very good and I've not experienced any dropped calls (unlike Google Voice in both cases).
I have an Obi110 and mostly use it for conference calls when working from home so as not to run up my cell phone bill (currently only about $22/mo with Ting). Our web conferencing system has a "callback" feature that initiates the calls, which is great as they count as incoming calls from a Phone Power perspective and are "unlimited" in their service plans. Speaking of which, I signed up for the $34.99/year special offer using the link from
obitalk.com. The account creation and provisioning process was very smooth and user friendly. However, after that was done I encountered two problems:
1.) I could not receive multiple incoming calls without having to reboot the Obi110.
2.) Incoming conference calls would drop consistently after 16 minutes (give or take a few seconds).
My setup was as follows: The Obi110 was connected to a WRT54GL wireless router (running DD-WRT) downstream from my Dlink wired-only router which was connected to the internet. For some reason the Obi110 had no problem using Google Voice with this setup, but it did with Phone Power.
Ultimately the fix consisted of simply bypassing the WRT54GL wireless router and connecting the Obi110 directly into my Dlink wired router. It was unclear whether it was the WRT54GL itself, or it being downstream from the Dlink router that Phone Power didn't like, but since the change I haven't had either of the above two problems. I figured I'd mention this anyway in the hope that it will help someone else in their troubleshooting.
We'll see if Phone Power goes back on it's "unlimited" promise in the long run as I tend to take a lot of incoming conference calls on those days where I work from home, but so far, so good.