7
I built a new site using XOOPS 2.2 when it was first released and had only 1 minor issue which didn't affect any of my visitors and was resolved fairly quickly. Seems to be stable from my experience. I picked modules that I researched to make sure they worked with 2.2.
That being said, if I was to upgrade my other sites using 2.0, I would stay within 2.0 (2.0.13.1, etc..), and not upgrade to 2.2 unless there is was a security issue or a functional problem that required 2.2, due to the fact that not all of the modules I'm using are compatible with 2.2 yet.
JC
JC