I'll chime in since I have had the spec'ed mac as tested for more than a year.
The first thing I will say is that for any type of performance analysis it will boil down to what you do with your mac. In my opinion, very rarely will users have the same requirements, specially in the macrumors Mac Pro forum. People use their Mac Pros differently, so bear that in mind. I will say how it applies to my case:
Barefeat's benchmarks are, I think, close to what I have observed CPU - floating-point-calculations-wise. I use the Mac Pro mostly on floating point calculations first and graphics second. The software that I use is not ported to OpenCL yet and I am unsure it will ever be, even though it is clear a 7970 or a number of 7970s would be faster that putting these x5690s to the same activity, I am stuck with CPUs for number crunching.
The benchmarks mean that for this type of work, the Mac Pro with these processors is indeed one of the fastest machines you were able to get up until recently. This has changed with the new generation of Xeons that just came out as these are faster. The new Mac Pro, as currently advertised, is going to be slower in this particular metric.
Even if you consider only floating point calculations, this is not an open and shut case in favor of the old Mac Pro with the x5690s for the following reasons:
- the new Mac Pro has a smaller profile that allows it to be in spaces that the old Mac Pro can't be in
- the new Mac Pro has, to my knowledge, only 1 big fan, whereas the old Mac Pro has at least SIX that kick in when you use the CPUs to their full potential: front fan, back fan, 1 fan per processor, PCI Bay fan and PowerSupply fan. The x5690s use 30% more watts than top of the line CPUs included, and even though the Mac Pro can handle them, I would expect the fans to obviously kick in sooner when fully utilized. This makes an attractive advantage if the noise of the new Mac Pro, as measured in dB, is half or thereabouts of the old Mac Pro at full CPU utilization. At the expense of course of being a tad slower (probably around 10~15% - again, only for floating point calculations.)
- Yes, the new Mac Pro has no internal expansion and that makes it look cluttered, BUT, what you gain in return is the ability to use the peripheral in question with any Mac that Apple will offer in December: MacBook Air, mini, any MacBook Pro, iMac. You can spend a litle more in a peripheral of choice, to be Thunderbolt, but in return you get usability with any current mac and some older macs.
Another thing a prospective Mac Pro tinkerer should take into account is that depending on your software, even if you only look at floating point calculations, these processors can be overclocked in another motherboard for about 10 to 15% worth. If you are willing to forego the Mac Pro and are willing to put in some effort, you may get an extra performance advantage out of the processors. If this is worth to you, only you can answer.
The last thing I want to mention is that graphics-wise (since that is my second requirement) the Mac has not the tweaked drivers that the professional windows drivers have. The silicon may be close to being the same (or even the same) as a desktop graphics version, but you will, very likely, not get the performance benefits that you get on the windows version, if one is available. This will be largely dependent on your application of choice. 3D design applications, video editors, sound processing, graphics manipulation, all will have different behaviors and take advantage differently from the video cards.
As far as my understanding goes, Apple has specifically mentioned that Final Cut X, Mari (texturing of 3D models app) will benefit for performance with the new Mac Pro.Their angle has been so far that you will get graphics performance, ability to handle high resolutions in multiple monitors, all while not losing ability to use graphics for processing. Even if functionality of the Dx00s graphics cards is on par with consumer AMD cards, you still get a lower noise output, a smaller profile and no tinkering on your part (two 7970s need an extra power supply in the old Mac Pro if you are going to tax them, which is the point of putting them in anyway.)
Whether all of the above makes sense in favor or against the new Mac Pro, is only dependent on your workflow.
Based on mine, I don't think the new Mac Pro is a step backwards. It has very attractive and real advantages, even at the announced prices.
The only criticism I would point out, are the drivers. The drivers really need to catch up with windows for the Mac Pro (either old or new) to be a clear-cut winner for a larger number of users.