I'm beta testing X4 on a Mac. It's not quite ready for prime time, but it's pretty awesome.
No boot camp, full compatibility with Mac OS. Also has revamped time/pitch stretching (no audiosnap).
All pro channel modules are now available as vsts, and my Mackie C4 FINALLY sees/controls them. There is no longer anything weird about take lanes, and the software comes with a live pony.