There's still the data migration issue. If you follow unstable all the time, an app may update its data files or databases at startup. Then, you can still roll back the binaries, but they'll just refuse to work (best case) or corrupt the unknown data format (worst case).

Yes, it's worth having ~hourly snapshots of your machine, using something like: https://github.com/digint/btrbk

You can still roll-forward specific apps - use the up to date ones if you really need to.