Apples core professional community has always consisted of artists. By that I mean folks that take pixels and make something amazing out of them on a daily bases. This might be photos, editing or simulations in Houdini or compositing in Nuke. Apple has always served the artist. In the nineties SGI was the king of doing this. Image compute speed and disk I/O at all costs. Matador and Cineon are some of the fastest image processors I have ever seen. The interactivity was great. These only run on IRIX boxes. The Foundry wishes its paint is as fast and interactive as Matadors was.
In 1997 SGI released the Octane. This machine was built for speed more importantly graphics speed. There was no 5.25 inch disk bay( they were all the rage). No CD-ROM drive. There were 2 full length PCI slots and 1 half length one. You didn't check Facebook on a Octane. There was a reason Sony Imageworks had stations for artists to use the internet. These machines were fast and even faster for drawing images.
In 2013 Apple released a new MacPro. This machine had SGI written all over it. Small, the GPU is fast. Fast disk I/O. The MacPro is pretty, but behind the design is a cooler core that can run faster longer. This means more power for a longer time from the CPU. Get what ever is in your head out on the screen no waiting. The Octanes GPU was a designated card from SGI. Sound familiar, it should the GPUs in the MacPro are also designated by Apple. They will also need the software developers to support OpenCL. From what I have read OpenCL is the the next step but it's happening slowly. Even Nvidia now supports OpenCL. No Optical drive is also similar. ThunderBolt is the new PCI slots and the internal drives bays.
The amazing thing about the new MacPro unlike like the Octanes is it can also email clients, make Quicktimes for clients, word processing and web browsing as well. A far step from the Octane. Sure you could check websites and send email on an Octane but nothing like how the new MacPro handles those tasks.
This isn't a machine for people who just want the fastest Mac for no other reason than being the fastest Mac. This is about solving image related problems and getting them done as fast and as precise as possible. The new MacPro isn't about text or fonts, it's not about Retina or your iPhone. It's not even about playing games. The new MacPro is about image compute speed which is really important to Apples core community.