One of the things that's been driving me crazy is whenever I organize my music collection (or more accurately, organize it more) I end up losing the data MixMeister generates for a file when the audio file gets moved to a new location. The next time I run BPM Calc it's as if I've never played it before and that means it has to be reanalyzed which takes forever.
One of the reasons I picked MediaMonkey as my digital music manager is because it was designed as a library management tool first and a player second. I have a fairly large collection of digital audio files in a variety of formats, types, and genres. I really needed a solution that would allow me to manage my collection in a personal way. I tried foobar. I've tried Winamp and iTunes.
One of the coolest things on the net for tracking listening habits is the Last.fm website. Just about everything I listen to is scrobbled and/or tracked there. The Desktop client is an awesome addition ‘cause it lets you tag, love, and otherwise interact with Last.fm without having to have their site up all the time.