I managed to do some SkyAmp development too, the category editing is almost done. It largely copies the functionality of editing lists. Copy/paste coding always works really fast, so even though I had little time, I did make some progress.
Oh, and Musicbrainz is truly, deeply, madly cool. They have a GPL'ed SDK available. I will add support for this thing in SkyAmp, along the lines of a dialog asking "10 songs did not have tags. Do you wish to identify them?" and then taking the appropriate action.