Bam! They have added watched folders:
http://lifehacker.com/5356619/itunes...-add-new-music
Well, since it isn't advertised and it's one specific folder, this isn't the true feature delivered yet -- apparently just a quiet test. However, with it implemented even in only one specific folder, there are a million ways to get this now to work as anyway could expect monitored folders to work with a few small tweaks.