Well I was in the Apple Store in Stratford Westfield (UK) today and they had a shiny new Mac Pro there.
Of course the first thing I did was fire FCP X - and you know what, it was 10.0.9!!! I didn't have time to find someone and persuade them to upgrade it. Which was a shame as I would love to have seen the machine at its peek. That said, it's still nice.
Everything is super fast a fluid - with the stock Apple material on the internal drive there was no lag in loading or drawing waveforms.
As I didn't have a lot of time I grabbed two clips (the Russian Arm against green and Helio footage) and stuck them on the timeline and applied a key. I was expect it to just zip though render but it wasn't as fast as if expected. More than likely this was due to the amount of projects open.
I duplicated this clip about 20 times - so the project that was about 10 mins long and hit export. Exporting to the internal drive at PR4444 took about 2 mins. Not bad at all but again should have been faster with 10.1
All in all If you have the money buy one. If I wasn't saving my pennies for an Arri Amira I would.