Can't say I haven't gotten my money's worth, but apparently (as of now) there are no other supported ATA options that work with Google Voice. Looks like I'm going to have to either just use an old cell phone, or have to actually shell out cash for a monthly VOIP service. Perhaps we may be saved by the third-party firmware option that I see people talking about over at dslreports.
My plan, is to keep using my Obi200 as long as it keeps working. If/when it stops, I'll try a third-party firmware option. If that doesn't work, then it will be on to using spare smartphones with the GV app...
If I lose the ability to use it with GV directly - and come to think of it, I should make sure it's working currently; I get so few calls that I'm not sure it hasn't gotten messed up somehow - my current plan is to keep using it with Callcentric in the middle, because I am still on the dollar DID plan they grandfathered me onto when their free tier ended, because I decided it was worth twelve bucks a year to maintain that fallback for either this eventuality or...well, in case I decided to start playing with pbx configurations again, really.
Creator has repeatedly stated that once these obi devices no longer work with Google Voice, the alternative firmware is not going to change that.
Once the obi 200 stops working, I was also planning to use multiple old cellphones around the house with the Google Voice app installed.
But since the Freedompop sim from Target offers free wifi calling, that now becomes an option for me to use with my multi-handset bluetooth cordless phone setup. Porting to Freedompop would allow me to use just one cellphone that would ring all the handsets. Downside is I believe I would only be able to call out using the cellphone.