Well it's based on BSD Unix, and I've run Linux (Mandrake, Redhat and Slackware) and Solaris x86 on my PC, so why not a little Mac flavoured BSD? Some of the enhancements they've done look pretty cool.
But I think in the end I'd go back to Windows NT.
(edit: Win2000 = WinNT5.0 if you didn't already know that)