I have around 15000 mp3 files representing over 500 albums and CDs in my library I have converted. I use mediamonkey for several reasons:
1) it handles very large libraries much better than other players I've tried
2) it has REALLY good support for editing tags
3) supports all the file types you'd ever want to use
That being said, it has its share of bugs and problems like any other software. Honestly, there isn't any perfect player (yet.) Things I find annoying with mediamonkey:
1) making playlists is a bit clumsy in my mind
2) crashes more often with most recent version than it used to
3) my media library got corrupted once and I lost all play history which didn't really annoy me too much, but it would some people excessively
4) the interface could use a lot of work in the looks/usability department in general
Good luck with your search. My advice is, install a bunch of them, use each for a week and keep the one you like best!