Before Spotify I had (well still have, but mostly untouched these days) large MP3 collection organized into Artist/Album/Tracks folder structure. This worked well for me and combined with Playlists meant that I maintained my personal "collection" of "Albums" as well as favourite tracks and Playlists for particular occasions / moods.
What I find these days is that I'm losing track of Albums, I have Spotify Playlists (although the flat Playlist structure tires me), but it's just not the same as having a personalized "Collection" of music.
Spotify needs to add the ability to build your own "Collection" (not Library, which is still track based), this should be organized however you like, but at least providing Artist / Album / Year drill-down structure (folders or not). It'd be nice to match this against existing MP3 collections and Libraries. The ability to tag playlists and collections (and/or albums) would also be a bonus.
What I'm getting at here is the missing part (for me) in Spotify is the ability to "virtualize" (cloudize?) my mental image of a music collection, which is shelves of albums sorted into some logical order (years, artists, genre, whatever), but mostly Albums, not just Tracks.
My 2 cents.
UPDATE 21/4/13: I don't seem to be "allowed" to embed images in my posts (sad). I've recently been using Google Music on a Nexus 10 and I have to say it has almost the perfect Album / Genre / Artist interface. I particularly love the way that in Artist view you see Albums stacked and they move subtly in 3D as you scroll. The only thing missing here would be Year and latest-added sort/views. Anyway here are the screenshots, this is DEFINITELY a better way to "visualize my collection":
http://community.spotify.com/t5/media/gallerypage/user-id/298076/album-id/3824
UPDATE 16/5/13:
Google Play Music All Access does this and more
Sorry Spotify but looks like you were too slow. Google just ate your lunch, dinner and breakfast for the next 10 years. Google Play Music All Access has the above functionality (add any album to "my collection") and more, including a MUCH better visualization of your collection, album based browsing and a considerably better radio implementation.
UPDATE 21/5/13:
Spotify ignore albums, again
It's pretty obvious now that Spotify have no interest in the albums or the art of constructing an album, don't they realize that most artists work for years to create a "piece of work" known as an album, not just a bunch of random tracks? Today Spotify launched their "Charts", which once again completely ignore albums... What with Google Play Music All Access and Rdio I think Spotify are going down the slippery fail slope to irrelevance.
http://charts.spotify.com/
UPDATE 1/1/14:
Looks like Spotify took this suggestion seriously and have been beta testing Collections for quite a while (yes, they made me a beta tester 😉 ) It works well and I'd imagine it'll be mainstream soon. (Keep giving the idea Kudos to continue to support it)
2014-04-25 Hey everyone! We’re excited to say this Idea status is now “Implemented”.
This month we introduced “Your Music”. Now you can save, organize and browse your favorite music. All in one place, across all platforms. For a glimpse of these changes and our new design click here.
Your Music is now available to users on desktop, web, Android and iOS.