I now have Jaikoz retrieving tags as genres from Musicbrainz, but not only that it can submit genres back to Musicbrainz. This means you can easily help build the Musicbrainz folksonomy, and you can use Musicbrainz to backup genres for your tracks. With a little bit of fiddling around it to easily tag your tracks with non genre information - such as the 'owned' tag.
The retrieve genres algorithm is as follows:
Get all tags for track
If any exist strip out any one we dont want using configurable blacklist
Favour tags that match Winamps genre list
If there are multiple matches pick the most popular tag one
If there are no tags that match Winamps genre list pick the most popular
If there are no matching tags repeat at release level.
If there are no matching tags repeat at artist level.
Only one genre is picked at the moment because most media players and audio formats only support a single genre so adding multiple genres doesnt seem to help much, but if you disagree let me know.