For those of you using Sailing media, try "itunes agent" it works really well with my N900, with around 2500 tracks (in exactly the same way) and its free.

The one issue I have with Sailing/itunes agent is the lack of playlist support - which is where doubletwist/Nokia media manager comes in. The issue is with an old itunes library its hard to detach from itunes. If only there were a way to talk with itunes seamlessly..

What id really love is music syncing over wifi (not possible yet..)