Because Zune isn't compatible with WP8 I'd imagine you would have to flash your phone manually. If you have a Lumia you can do it using Nokia care Suite but Navifirm is about to be shut down (if it hasn't already been) so unless you have a copy of the previous firmware already downloaded you're pretty much stuffed. I don't know where firmwares can be obtained for HTC's or Samsungs (sammobile.com aren't hosting firmwares for the Ativ S).
It's a shame that there is no easy option to restore to a previous version. What's the point of having all these backup and restore options if you can't do a basic good old Windows restore!
Agreed. The ability to roll back in WP7 was an excellent feature so to have this feature removed is a massive backwards step in my opinion. It's going back to the days of Symbian where you're stuck with the firmware you're on with the only option to manually flash and run the risk of bricking your phone.
well, depends on your device. With a Lumia, you can just do it with the Nokia Care Suite.
I had to restore stock 8.0, because Portico failed to install (error 7008000d), so I chose restore (not only refurbish), selected the Firmware and followed the step. It was easy and solved my problems