I personally think foobar2000's fairly excellent. Flexible as hell, both in UI and in functionality. Quick and doesn't feel bulky at all. It's honestly the piece of software I miss most when I'm on my Linux install.
It has been named in this thread before, but you might not have seen it. I used to run foobar under wine, but honestly, deadbeef[1] works better from an integration point of view (global shortcuts, GTK etc.).
I tried iTunes back in 2009 when I was trying to get some music off of an iPod. Worst user experience ever. When you have to watch 5 minute video tutorials on Youtube to figure out how to do something, your user interface probably sucks.
Also, yes, the bloat and the constant updates to support the bloat.
You put music on your iPod or your remove it. It's not meant to bring around to your friends house and take all the music off of it and onto his computer. This is by design.
It lacks separation between the concept of a library and a playlist. Winamp has its Media Library which you use to browse and search your media. You then play what you want by putting it in the Playlist Editor. Whereas iTunes and every other media player just plays everything in your library starting with the file you clicked on.
[EDIT] Others have covered bloat, install issues, and its updater.
