I've used EasyPose Underground with both Parallels and VirtualPC using WinXP as the guest operating system.   Works great.

Haven't found any bugs in the current version worth complaining about.   I suppose it might be nice to add more support for "conformingTarget" (e.g. mastering ERC from a "standard" but not loaded in EPU figure), but the "Deep Slave Editor" does well enough for that.

Support for the "valueOpKey" structure would be great.

If you need someone to test Macintosh (via emulation) compatibility, I'd be happy to do testing for you.

Cheers!
-Kerwin