Amex did some type of calculation, resulting in a partial, although substantial refund of most of what I paid, although not all.

On the other hand, I was just sent a letter offering the chance to sign up as a creditor. I probably won't get a cent, but it might be worth the price of postage just to try it.

I had charged my subscription to Discover, and they were apparently successful in cancelling the charge as well. Since SunRocket technically doesn't owe me anything anymore, I tossed the creditor letter . . . didn't think I'd have a leg to stand on.

I still have a SunRocket Gizmo, though. Is it good for anything?

You can unlock it and use it with a different provider.

I'm not likely to jump back into a VOIP service subscription anytime soon. Is there anything else it's good for? :D

If, for example, my (small) corporate office on the west coast elected to install a VOIP based telephone system, could I use the Gizmo as a terminal for an "extension line" in my home office on the east coast?

Yes. It should be able to be used like that. I've unlocked my gizmo but I've not used it for anything as the provider I moved to supports my direct use of Asterisk and I've now got a bunch of VOIP phones. If they do install a VOIP system make sure that it can handle standard SIP clients. There are a number of proprietary systems out there.