Until I registered for this site to be able to participate in the forum, I had never used the Obitalk site for anything. The OBi100/110 is a complete self-sufficient ATA that doesn't need the website for anything, as long as you're not using Obitalk and are comfortable configuring your own device. I migrated to it from another (Grandstream) ATA with my SIP account and set it up manually.
As it contains a full-featured web server you can log into on your own network, you've got easy access to all 6 trillion settings (well, probably less, but it seems like a lot). The IVR menus also give you access to some of the settings. The 160-page manual is pretty good, but a little jargon-heavy in spots and not great if you're not already familiar with some of the concepts.
Adding GV to my setup and kibbitzing around with the dial plan/key maps gave me free outgoing calls on GV and one phone to receive both GV and SIP calls. With yesterday's outage, I just used the Google Voice website to initiate the calls to my SIP account, the same way I did before I bought the OBi100 4 months ago.
I lost nothing in this scenario, except some frustrating time spent trying to get my OBi to reconnect to GV before I checked this forum to find this was a systemic problem.
Kudos to OBihai for quick response. I contrast that with my experience with my Verizon landline last year. It was out for days every time we had a heavy rain. Some service box in a manhole was getting flooded. The last time, it was out for FIVE WEEKS because a) there was a strike, and b) they had my phone on the list for repair in the wrong manhole. I'm all VOiP now, and much happier, and richer for it, too.