The thing is fast. The SSD tests at 800MB/s write and 932MB/s read. The external drive is 318MB/s write and 370MB/s read, which is as fast as a cheap SSD. 60GB/s memory speed (1.867GHz x 8 bytes wide x 4 way interleave). The Intel E5 is fast in a different way than the i7. Even though it is only running at 3.7GHz, it doesn't slow down when you add more applications. Something not talked about much on the i7 is the fact that the clock speed is dependent on the number of active cores and the temperature. An iMac or other Intel PC with the Core-i CPU may run faster in spurts than the Xeon E5, but the Xeon just keeps chugging along no matter what I have running. Like the big servers at work - they don't have phenomenal clock speeds, but they don't bog down under heavy loads. Unlike the reviewers' test systems, which test running a single application, I run my computer with all kinds of things going on - including about a hundred system apps and drivers. The idea that a single core will run a single application as fast as a multi-core CPU is hogwash. There are all manner of activities not associated with that single app taking resources away from it. Anyway...
Money well spent. Lots of money. $2.8k for the Mac, $680 for memory, and $400 for the disk drives. We paid $3500 for the top of the line iMac five years or so back, so this wasn't extraordinarily expensive. The money spent on the 4790K isn't a loss, either. That box is now running Windows 8.1, and doing (of all things) Mac program development with Embarcadero's XE7 (C++ Builder). I knew Windows 8 had to be good for something.
Left to right: 2TB My Book backup drive, Mac Pro, DVD Drive, My Book Velociraptor Duo, 1TB backup, CentOS on i7-2600K, 1TB backup, Windows 8.1 Pro on i7-4790K. The two i7 boxes are water cooled. The whole mess is sitting on floor tiles with soft silicone rubber bumpers under them to cut the noise. It works. The Mac Pro is practically silent already, but the water cooled boxes make a little noise, especially when they are backing up (fan speed vs. temperature). The shelf is not bowed - the camera lens is.
Not shown are the Macbook Pro and the two Mac Mini's. The i5 mini is used as a print server, and the i7 as a backup in case something happens that requires another Mac. The Macbook Pro belongs to the company I work for.
I don't need any more computers.
I've had a few of months with the Mac Pro and I have decided that it is even better than I thought. I have it set to spin down the external drives when they aren't being used, and although it sometimes adds a slight delay when I save a file, it isn't at all annoying. When it wakes from sleep, there is a delay in network access while it brings the network back up. Overall, the machine acts like a big rock rolling down a steep hill. Nothing can slow it down.
Although it can handle three 4k or six Thunderbolt displays on its two graphics cards, it can't handle 3 HDMI monitors. That is apparently because only one graphics card is used for the main user interface, and it has just two "passive" (HDMI/DVI) outputs. If I add a $30 active HDMI/DVI adapter I can run an additional monitor. Or if I add a Thunderbolt monitor. I would love three Thunderbolt monitors, but even one is more than I can justify. And I share monitors between the Mac, Linux, and Windows machines, so I need monitors that are compatible with all of them. The Windows box has a display port connector, but I haven't seen a display port switch.