Playlist: a big window will do.
Media Library: I do have an increasing amount of music. Why does this necessitate bloated crap like a music library? We've had these things called directory structures for decades, dude.
Artist/disc/songs, and flac folder if new enough.
User-friendly: you double-click on a song, and it plays. right-click, and you get options (like ABX, ReplayGain, transparent tag editing, including multiple files, CD writing, header fixing, etc.).
FB2K offers everything necessary, other cool stuff, and a much better interface than iTunes, except for iTunes' search, which does rock.
So, face it: many people don't want the same things others do. You can use iTunes. I won't. Why? Because as much as you think other players suck, I think iTunes sucks, as do others.