doesn't work with complete reinstalls of FF Rated 1 out of 5 stars
Maybe this checkCompatibility 1.3 add-on works with automatic internal updates of FF(?), but not with complete reinstalls...
I had it enabled in FF 18.0, uninstalled FF while keeping my personal data and settings, then installed FF 18.0.1 from "Firefox Setup 18.0.1.exe" (19,821 KB). That's my usual procedure. I don't trust the automatic internal updates which often cause problems in my experience.
My add-ons were checked for compatibility and one of them was disabled, so it didn't work (had no effect). That limitation should be made clear in the description.