Sharing OS X iTunes Library with Bootcamp?
This solution may very well not be to your taste, but the simplest thing I can think of that doesn't involve the phrases "disk partitioning" or "file permissions" would be to sign up for iTunes Match and match / upload your music collection, thereby making your music available to both your Windows and OS X partitions as though they were simply different devices (which, for all normal intents and purposes, they are).

I recognize the downsides to this approach:


The service isn't free (~$25-$30/year, depending on location), or even necessarily available in all countries
If you have a large library, you'll be using a lot of disk space to keep what are essentially duplicate files in each partition


But the result is a fairly painless and reliable solution, which does indeed keep your playlists, rating, and play counts in sync.