I've been meaning to work more on this, but my free time is fairly limited. At the very least I should probably put my script on GitHub (although it's far from groundbreaking).
For me, one of the pain points is quality of metadata. It's all very well collecting genres, tags, and similar artists from a service like Last.fm, but you need to be reasonably confident that they align with your own ideas about music. Since everyone's ideas about music are different, this puts you in a tight spot.
rateyourmusic.com's genre system works pretty well, it's based on user voting on genres for an album (genres are selected from a list, which is constantly being updated by democratic process too)
For me, one of the pain points is quality of metadata. It's all very well collecting genres, tags, and similar artists from a service like Last.fm, but you need to be reasonably confident that they align with your own ideas about music. Since everyone's ideas about music are different, this puts you in a tight spot.