I've got a large library of 18000+ tracks that I regularly sync between my desktop and laptop. On the surface of it, Tuneranger's features is ideal. But after many months of use, and lots of feedback to the author, this app still has serious problems:

• Frequent crashes
• Trouble connecting over the network
• Poor UI responsiveness (developer doesn't understand threading)
• Maxs out CPU for long periods, shortly after startup
• Duplicates 1000s of tracks!!!!
• Does not fully sync metadata for all tracks (I constantly have 1000s of tracks where the metadata is different on desktop and laptop machines, despite numerous syncs)

That said, the closest competitor is SuperSync, which, frankly, I found unusable. None of these iTunes sync apps are close to finished.