This is a spectacular idea! I'm very pleased you're working on this. Now that I have my empeg, I really don't listen to anything else and things get "stale", as others have commented.

Regarding recommendations, I think it would be very cool if this feature created a "recommendations" playlist at the root level, with Artist->Album->track underneath that (optionally?). Anyhow, imagine if, under "recommendations" you had "influenced", "roots", "similar" playlists (again, optionally enabled). Then, by default, when you invoked the process you would get a recommended playlist with sub-playlists for each of the recommendation types. It would also answer the question, a la Amazon, "why was I recommended this?" You would know based on where the entry appeared which recommendation algorithm was used for that particular track.

Sorry if this seems incoherent. What I am saying is that the default should be all three recommendation types, categorized in sub-playlists.

Jim