Tuneranger is the only game out there, but it has plenty of issues. I just could not get it working reliably enough to trust it implicitly as I can say Synctoy or Chronosync for file syncing.
Having iPhone and Touch, I'm locked out of using better sync / media management software than iTunes under Windows - so after struggling here and there, I gave up trying to keep Win/Mac iTunes in sync, jacked in my Windows iTunes library and dedicated one of my Pros to iTunes syncing duty. This Pro is the only OS X machine attached to my main shared music library.
I did also have to give up trying to sync playcounts between computers but it hasn't been a big deal - I only really need to keep tabs on that for portable use, which means for me it's not a big deal having the info sitting only on the Pro which is dedicated to syncing with the iPod.
This doesn't mean I can only have music on the Mac - it just means I can only change the contents of the iTunes library (and therefore the shared music library) on that particular Pro. The actual folder that the iTunes Library music is stored in on a Windows server.
Then on the Windows machines I use j.River Media Center (the budget minded can use Mediamonkey Gold for $20, half the cost of j.River) which hooks into the shared library and has the capability (unlike iTunes) to automatically monitor changes to the library. So all changes made by the Pro in iTunes to the shared music folder, Windows machines can automatically monitor and register changes.
Having iTunes installed in each of the Windows machines you want to use to listen to purchased tracks and having each machine registered to iTunes will mean that Mediamonkey and j.River Media Center will be able to play back secured iTunes Store purchases.
You'll notice that the above (auto-monitor of music library additions) is only possible on Windows machines, so you really have to manage your iTunes library on the Mac side however you try and do this. Since your Mac is a portable, this complicates things since your music needs to reside on the Mac itself... and you'll need to bring in Chronosync or similar into the equation to sync Macbook-stored music library to the Windows machine.
A monumental pain, no?
Basically the lesson of this is that iTunes+iPod is great for making music a no-brainer experience if you only have one computer. It makes it a nightmare if your needs go beyond that.