[drivebyacct2]

>Is anyone using it fulltime now and happy with it?

Yes. I exclusively use it. The Messaging (SMS) app is disabled on my phone, I don't pay for SMS service and my friends and family only know my Google Voice number.

The only usability issue I've had wasn't even a problem for me. My Mom's RAZR was slow to receive messages through her Google Voice number. Amazingly that went away when it got updated to ICS/JB.

Taking calls through Gmail (I have a bluetooth headset I use anyway, I get lazy from holding up my phone) and sending/receiving SMSs from any browser is great too.