I have been using Google voice with my OBIs for a couple years now, never had issues
I have three OBI devices, 1 - 202 and 2- 110 they all work great.
I signed up for PhonePower a few weeks ago, started with their $35/yr plan but found the 300 mins/mo was not going to cut it so I upgraded to the $60 unlimited plan.
Phonepower spoofs the Google voice number so people can still see that number when you call. I have forwarded my Google voice number to the new PhonePower number. Phonepower also has setting for low bandwidth if that is an issue for you. They also have a BLOCKED LIST for "those people you want to block"
and SELECTIVE FORWARDING. I have found the calls crystal clear with PhonePower and very feature rich.
I have one of the OBIs in the Philippines setup with a local number which makes for very cheap international calling. I have been able to keep the firmware up to date from here which I really like.
Anyway PhonePower gets two thumbs up from me so far.