From what I read on the community, it seems to be pretty stable. Expect a few bugs though, like one use reporting Google Pay not working for them.
Once you opt in and upgrade the os, and later if you decide to revert, you may encounter issues.
The beta is for the S22 series. At least that is what I go on my invitation from the members app. However, I am not trying any beta. The S22 series has had enough issues on the stable Android 12. The beta by definition is not a stable version.