Here is my editing room as it is now.

Notice the Power Mac all the way to the right.
The latest and greatest Mac, and it SUCKS.
It does not even come close to the machine all the way to left I just built.
Next to the new PC build is my i7 920 which was not getting what I needed done fast enough.
When I tell a person something, I tell no lies. I have done a side by side comparison, and there is no comparison.
Mac has dropped the ball by not installing i7 cores into their top of the line machines.
I edit all of my Canon 5D MkII and SONY EX1 footage with the new beast.