So, I'm not the target audience for the Mac Pro; there's a couple of things about it that I find interesting though. Not the aesthetic, especially - which admittedly is quite cool all the same. We've seen computer's like the Piston and the Ouya console recently, and while this is the first machine of it's performance level to have such a small form factor it's interesting for it's practicality more than it's aesthetic quality from my perspective.
The first truly interesting thing, for me, is the reliance on Thunderbolt for expansion. Apple have made the judgement that thunderbolt (essentially an extension of PCIe) is fast enough that the old paradigm of internal expansion can be eschewed. There's an inherent cost in the external expansion approach: each external device must have it's own housing, Thunderbolt controller and potentially it's own power supply. Though as a friend of mine commented, a media producer by trade: "This is the first machine in year's that I've wanted to place on my desk"; a lot of external drive enclosures and such are pretty in their own right these days - so those with the inclination could literally tailor their computer to their aesthetic preferences in a way unlike any before.
There core components of the machine are still internal (logic board, CPU and RAM) and we're not quite in a position where external graphics processors are a reasonable option. However thunderbolt is more than speedy enough to make external storage and innumerable audio and video tools sensible options for this approach.
The future of the workstation appears (at least in Apple's eyes) to be a number of chained devices and displays configured (and easily reconfigured) according to your immediate needs. It's success depends on a so-far sluggish uptake of thunderbolt by device manufacturers - something that is on the increase and may well be stimulated by the Mac Pro launch later in the year. It remains to be seen if manufacturers will really capitalise on thunderbolt as a new primary form for mainstream hardware, bringing down the price and improving choice.
The other interesting thought, for me at least, is that the Mac Pro is exceptionally portable. It's no laptop or tablet but if you need to work somewhere else, you can grab the Pro (by it's built in handle), the hard drive unit you need (or whatever) and go. The construction of the machine should be sturdy enough that it will travel in the back of the car quite happily and so long as your destination has a usable screen you're good. It really leaves only the iMac as a stationary workstation - MacBooks being portable by nature and the Pro now happy to sit connected to any available thunderbolt or HDMI display that's available. Even the Mac mini is small and sturdy enough to pack in a bag when you're on the move.
It will be interesting to see if portability is a direction that Apple will pursue in future iterations, or if it's really just a happy coincidence of the other design choices.