Well you can do a full binary install from the setup script but a lot of the configurations have changed, so I’m not sure how that affects those. Before you do an update its always good to backup just in case. I personally just use a fresh SD image and reconfigure things.
I’ve just updated from version 3beta2 to version 3beta4. It went a lot better than I expected. So far it looks like the only files i’ve had to change back are es_systems.cfg, gngeorc (the neogeo config file) and then copy across my uae4arm amiga adfs and conf files.
Other than that it looks like an easy and pain free update. I really like the way controls seem to have been integrated. This is a big big improvement. Time will tell though.
If you’re updating from version 2.6 then expect a massive headache if you’ve heavily modified various congfigs to get them running correctly. In such a case it’s really just worth starting agaion from scratch.
But going from 3beta2 to 3beat4 seems fine (with a few precautions take first of course!).