There are features still missing in 2009.5 for Mac, in comparison with the 2007 for Windows version I had running under Parallels:
- no multiline notation window
- no repeats/codas/1st-2nd endings dialog
- no simple marking and looping of any arbitrary section
- no choice of jazz or regular fonts in lead sheet printouts
- no chord symbols like a triangle for Maj7 in lead sheets

When I first bought 2009 for Mac I found this pretty annoying, but in the end I decided to just work with it and see what happens. And you know what? After a while I found I was getting things done fine in the Mac version, eventually I de-installed the Windows version and I've never missed it. I still hope those features I mentioned above will be coming soon in the Mac version, but in the meantime it's just not worth the hassle of working with Windows.

So that's my advice to jholman - since you already bought 2009 for Mac, give it a proper trial by using it exclusively for a while, that's the only way to find out what you really miss.