Still doesn't make sense because the gpus dont have a SDI port = no genlock. So for video editing, it's only good for offline tasks as a render box and editing. But the cards are under-powered too it's not even good for that. The gpus dont even have ECC (the pc version of the cards do). Also when the macpro was released, it didn't support 10bit color (it might now not sure). And the gpus are basically non upgradeable under osx. For windows you can use a eGPU but not really. And if it was a render box, youd probably select a different cpu than offered too.
Really makes no sense unless you HAVE to have osx. The GPUs were maybe attractive at release, but not anymore.
Im tearing it to shreds, there might be some uses out there but for most it doesn't work out I think.
To give an idea how ridiculously under-powered it is for the price, consider one could have a fully loaded pc with quad titan-x gpus (not workstation cards, but the macpro really isnt either) with 18-24 core cpus and still come out ahead
Some comments:
1. Yes, some Windows pro graphics cards include SDI, but it's far more common for a separate interface to be used. These are typically PCIe these days, so these also exist as Thunderbolt devices (since Thunderbolt is just PCIe protocol over the DisplayPort physical interface). So if a Mac is to be used with Final Cut Pro for broadcast, it's common to add a Thunderbolt SDI interface. But I'm pretty sure most video editing is done offline, without SDI. Broadcast is a very specific subset of video editing.
2. The 10.11.1 update to OS X added deep color support if the hardware is capable of it (finally). (Many people installed the update and found their setup to suddenly be running in deep color mode, since any halfway recent GPU supports it. It's now usually the displays that don't support deep color.)
3. The GPUs in the Mac Pro are essentially not upgradeable, but that's because they're a weird form factor. It has nothing to do with OS X, which has supported off the shelf GPUs since the 10.8.5 update. You don't get the nifty Apple logo on startup when you use a PC graphics card, but once the OS has loaded the graphics drivers, they spring to life and work using native drivers. (I use an unmodified PC AMD HD7970 in my 2008 Mac Pro, and it works perfectly.)
4. The primary difference between "pro" and "gaming" graphics cards on Windows is — other than the presence of additional ports sometimes — the drivers. The GPU chips themselves are identical, but on Windows, there's a huge difference between the gaming drivers that have had the living daylights optimized out of them for speed, at the expense of stability and mathematical accuracy. The pro drivers on the other hand are optimized for stability and accuracy, but dispense with the speed optimizations. On the Mac, we don't have gaming drivers at all — we're always running the pro drivers, in essence. That's why on the Mac, many pro 3D apps like Maya run on consumer GPUs, while the same app demands a pro GPU on Windows. ECC VRAM is certainly desirable (especially for non-graphics compute tasks), but I can only surmise it's not essential for video rendering.
In essence, Apple built a box optimized for Final Cut Pro, which is (as far as I can tell) much more efficient than other editing suites (regardless of platform), insofar as it's so good at leveraging hardware acceleration that it usually ends up doing in real-time what other programs have to render after the fact.
For any task other than video editing, the new Mac Pro simply makes no sense whatsoever.