I find great satisfaction in auditing my music collection.
I've been collecting music in MP3 form since the mid 1990s. Some time ago I went through and updated a lot of album art and track information, but it was haphazardly done and didn't take into account lossy vs. lossless versions of the music. In contrast, looking at my database today I have 2,053 artists represented across 10,583 songs, where 9,026 (85.3%) of those songs are as "right" as I can make them. This means that they're lossless where possible, they have the highest-resolution artwork I can find for them, they all have lyrics where I could find them, and all their information (song titles, genres, track numbers, etc.) has been vetted through Wikipedia.
Today I ripped an album (The Fine Art of Surfacing by The Boomtown Rats) to lossless ALAC files, found some decent-sized artwork for it (600 by 600px) at the Album Art Exchange, checked to make sure all the track information synced up with Wikipedia, and added lyrics courtesy of LyricWikia.
Then I looked at my "yet-to-be-right" playlist and bought albums by Billy Gilman (Dare to Dream) and Blind Guardian (Live), and a Christmas compilation album called Stockings by the Fire to replace lossy versions I identified in my database. They'll arrive soon thanks to Amazon Prime, and I'll repeat the process with them once they're here.
I also enjoy making playlists for my music. I have playlists for artists, genres, decades, as well as the default iTunes playlists like "Most skipped" and "Longest songs". I'm collecting into playlists all the songs that comprise The Axis of Awesome's medley song "Four Chords", as well as all of The Nostalgia Critic's Top 11 Villain Songs. Then I have playlists for Star Trek songs, Firefly songs, Disney albums, Pixar albums, other soundtracks, James Bond themes, and more.
This is all immensely fulfilling for me; that it pushes all the right OCD buttons is a huge part of it. I also listen to a lot of my music in the car, and I appreciate having all my music error-free, catalogued into playlists, listed under correct authors, and genre-labeled for my ease of playing while driving (though more often than not I find myself listening to my entire collection on shuffle anyways).