Smart Home has been selling their new INSTEON Hub v2 for just $40, so I couldn't resist upgrading my older hub. (Note that the new one is smaller and otherwise improved, but no longer supports X-10 devices, if that's important to you.)
When the new Hub arrived, I couldn't find any information about how to migrate from my old one. Worse yet, the iOS app would only associate with my old one, making the new one nothing more than a paperweight. I contacted Smart Home for help, but didn't get any reply.
Well, after some poking around in the slightly clumsy app, I discovered part of my answer. To add the new Hub 2, in the app, go to the "House Management" section of Settings. From there you can add the new Hub, which is quick and painless. (You'll need the Hub nearby as it involved scanning the QR Code on the bottom of the unit.)
There doesn't appear to be any way to migrate your devices from one hub to the other, though, so you'll have to re-add each device individually. Not a fun task, particularly for light bulbs that are inaccessible.
With the sad demise of Revolv, the INSTEON Hub is now the best choice for setting up quiet, simple, and easy home automation. It's not sophisticated enough for a DIY enthusiast, but for most, it's the way to go.