The big problem with a Mac is that its price can't justify the performance anymore. It used to do that when Mac ruled among audio apps, but PCs are already up at the same level. You can't deny that anymore, because alot of applications seem to have a PC release first these days (Rebirth of the top of my head for example did this). The reason (no pun intended) for this is PC numbers vs Mac numbers, not audio performance.
I'm far from anti-Mac, but I just don't buy the hype with those prices.
-tek