I had one in my shopping cart the day they were announced, but at checkout it appeared the configuration I wanted -- Hex-core 3.5, 64GB RAM and 1TB flash drive -- was already then slated for a February delivery. So I decided to wait until they were in the main pipeline.
In the meantime, I needed a new laptop, so bought a 15" MBP Retina. I am currently using it as my main processing machine, added a 4 bay Pegasus TB2 RAID enclosure, and 3 2-bay USB3 raid enclosures for redundant back-up purposes. Also bought and connected it all to a new Eizo 27" monitor. I am very pleased with the MBP as a main editing machine; it's working so well I may not bother with a full on Mac Pro.
Caveat: Bob has a the same MP on order as I was speccing, so will hold off my final decision until hearing his real-world performance reports. (He also has the same MBP, main RAID box and monitor as I do, so he'll be a good 'guinea-pig' for me.)