Playlists really don't organize your music. A playlist, smart or otherwise, displays music using existing meta data and preference criteria.
Populating genres, grouping, year, PBM, etc. and then using those data for smart playlists is the key to a well "organized" iTunes library.
I use Jaikoz Audio Tagger (
http://www.jthink.net/jaikoz/jsp/startup.jsp) to help populate the tags. It works great and integrates with MusicBrainz audio id service.
If you have a Mac, try Tangerine.
http://www.potionfactory.com/tangerine/. It makes playlists based-on the BPM of your music.