I am finding the defense of the iMac as tool for serious professional 3D/Scientific/Medical/Simulation/HD/Film/Audio applications hilarious. Can you get away with it in a pinch, or as a prosumer? Maybe, maybe not. As I've said before, if Apple plans on killing off the Pro, or coming out with some idiotic modular design, then just say so. Then those of us who invent new things that improve your life, even save your life, entertain you, and solve complex problems, etc. can plan for the future of our labs and studios, then concentrate on doing our work, instead of fretting over what we are going to do that work on.
At current 20 to 25% off sales, those HP Z620/820 boxes, with 3 yr. warranties and 24/7 USA based support are starting to look pretty good right now. I made a pretext call to HP pro support to see how it compared to Apple. They were every bit as good. I checked out the new 620. It too is a well built/designed machine (other than cable management, which is easily fixed). I spend half of my time in Boot Camp anyway. I have one or two of everything Apple makes except the iPod, and a large chunk of their stock. I love all of those. But, the only reason I can afford them is because the Mac Pro makes me the money needed to buy them. If you are leaving me Apple, just leave now so I can go find someone else who does care and will happily meet my needs.