That is the only show stopper for me right now – I can’t sort music in any other way than playlists. I can certainly make playlists, and I can share them, but I cannot tag music for my own part, for easier searching, or for correcting and extending spotify’s tagging.

Spotify’s metadata has a few shortcomings – like for classical music they typically don’t list the conductor of the orchestra, and the composer is often part of the title field of the album.

I’d be happy if this was a per-user feature, so that I only see my own tags, but it would be even better if one could share sets of tags with other, or use crowd-tagging for adding more metadata to music.

(As a sidenote – Spotify lists little or no metadata about music, which is a sad thing.)