I have found the combination of Obi202, PhonePower $35 ObiHai account, and GV about as smooth and easy as anything could be. We mainly wanted the PP account to preserve our landline number, but find the PP service preferable to GV for most calls. Having both GV and PP provides a lot of extra capabilities. (Plus unlimited GV calls to my spouse's Canadian relatives, although the 300 minutes of Canadian calls on our PP plan is more than enough.)
The Obi arrived 12th of December and I immediately provisioned it with GV on SP1. That worked perfectly. Also signed up with PP the same day from the ObiTalk page and provisioned that on SP2. Also entered an order at PP to switch our landline number. However, our landline was still connected so, after testing, I disconnected the DECT base unit from the Obi and connected back to house wiring for receiving calls. Downloaded and installed the PP Softphone on several computers and found it worked great for outgoing calls via PP. I also downloaded and installed the GV hangouts app to use as a GV dialer. The PP account was set up to ring the GV number in case the Obi isn't talking to it.
On 21 December, Our landline number port to PP finally completed and I moved the DECT phones to the Obi202 Line 1 input.
Outbound calls from handsets prefixed with **1 go via GV, other calls from handsets go via PP. Calls to either GV number or PP number ring the handsets. Calls to the PP number ring both the softphone and the handsets. I find having both is great for testing. For instance, I can use the GV hangouts app to dial our PP number to test changes to the Obi settings.
I don't know what additional ways these could all work together, but I am extremely happy with what I have right now. At one point (after disconnecting landline at the premises junction) I tried connecting the DECT base to the Obi via the POTS house wiring, but found that resulted in horrible static on the dial tone, so I use it directly connected to the Obi.
As always, YMMV.