I used iTunes for a long time with a library of around 1,000 albums. If you weren’t too lazy to add proper covers and ID3 tags, it was actually pretty enjoyable to use – especially together with an iPod. But the problem is that iTunes imposes a very “flat” structure on your library, while for some collections a hierarchical folder/subfolder/file structure just works much better. Not to mention that you can keep all kinds of related files alongside the music itself – booklet scans, lyrics, interviews, links, PDFs, and so on.