I would like to know too as me think iTunes works really well, especially with iTunes Match. And most critique about iTunes tends to be more emotional than logical.
PS: Try to write an organizer that is snappy with 20k+ tracks… My bigger iTunes collection works just fine.
ITunes is still worth it IMO because if you decide to switch between serato and traktor both can read from iTunes library so you don’t start from scratch.
And if you set this later via the iTunes preferences it will re-organize the file structure based on the settings so you don’t need to worry about wrong layouts from day one being impossible to fix.
Anyway, Traktor reads the iTunes hierarchy information (folder/albums) so I seldom if ever look inside the iTunes music collection on the hard disk.