iTunes is bloated, limited, and very slow with large music libraries. Not to mention its constant nagging to download 80 MB updates for every bug fix. Check out J River's Media Jukebox (free version for music only) or J River Media Center (adds video, photos, etc). A much smaller, less resource intensive app, which nonetheless is far more functional and configurable, particularly with respect to tagging. Handles very large music collections with superb performance. Windows only, though.