OK, I've been playing with the plugin for a while, and here are some things that I have found that may help you in tracking down problems.
First off, I haven't seen ANY of the problems that GHammer is having. Navigating and importing work, and tags seem to be added to the library. Playback is fine with and without using the WVC file. So far, so good.
As I said before, though, trying to update the tags in WV files will lock up MC solid. Even when it seems to update the tags, if you exit MC, you get a dialog box that the tags are updating and THEN it locks up. The only way out is to kill the process in taskmanager.
Burning CD's works as expected, assuming that it decoded the WV + WVC when it decoded for burning.
And as a nit, when WV files are imported, existing tags for DISCNUMBER and CONDUCTOR aren't imported. All other tags seem to be read fine.
Hopefully some of this helps.