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Let's see what's good. The internal design is nice and cable-free, let's keep that. The cheese grater mesh and the aluminum is great for airflow and cooling, let's keep those too. The elevation is good. Another keeper.
Now let's look at the stuff that's less than perfect. The power socket way up near the top? Dum-de-dum. I don't care where the power supply is - get that thing moved. 3 USB ports on the back? Are you kidding me? Is this an entry-level laptop or a professional desktop? Try 6. Two FW ports on the back and two on the front? Um, few if any need two temporary FW ports and nobody wants a permanent setup with ugly cables hanging off the front. Try 3 back, 1 front. Now, what about those giant handles? They're great when you need to lift it once a year, but for those 364 other days a year they're in the way when you want to place peripherals on top of the machine. It's like having a suitcase with a giant handle that won't fold away. Inventors solved that stuff 500 years ago. You can do it too. Finally, aesthetics. Any chance of throwing the customers a bone here? Perhaps a black Apple logo and some black trimmings to bring it in line with every other Mac in the lineup? How about those ghastly CD tray squares, they look positively retarded, any chance of slot-loading drives or do you still have to cater to the 0.000002% who have this mini-CD they simply must insert every day?
These are just suggestions and you might not agree with them at all. But please don't suggest that the Mac Pro can't be improved or that a fresher look would come at the expense of function. The Pro has just as much room for improvement as the old Mac Mini did. The difference is that Apple hasn't stopped caring about the latter.