I like to keep my iTunes library as small as possible. I'm at 723 songs at 4.6GB and shrinking. I guess I'm a little picky, but if I don't like the song, I rate it 1 or 2 songs, and take it out. Why would I keep it if I don't like it? I constantly get new music to try, delete what I don't want, and move on with more.
I used to be anal about keeping whole albums in lossless formats, but I've realized that it doesn't really matter. Plus I like having all my songs on shuffle and me enjoying every song that comes up.