Generally, we’ve found only one problem with running K2 under WordPress 2.2, which was just released, and that’s a problem with using our sidebar modules with the now built-in widgets solution.
For now, here is the solution.
Contrary to what you might think, K2 isn’t quite dead, as evidenced by the changelog. In fact, it’s worth subscribing to that feed, to keep up with code-changes and compatibility issues, all of which will be listed in there.
WordPress 2.2 is coming up, and I figure we might do a release for that (which requires some twiddlin’ with the sidebar modules, due to WP changes, so that’ll be fun).
Until then: We live.