I'd be curious to know what your computing needs are that the nMP felt deficient for.
Also, no offense (or offence, since you're in the UK) intended, but that is one ugly box on the inside...I've been using Mac Pros for so long that I forgot what a tangled mess normal PC cases are like. I'm also not sure I could ever trust a hackintosh for professional work.
The reason it looks a bit of a mess inside is that I had to run across a molex lead to power the USB 3 card at the back, I now have an alternative solution which has removed that, and there was a red SATA lead running down as I did not have the SSDs in a sled (Did not have a 2.5 to 3.5 convertor for the sled to hand), now those flyleads are removed it is back to being neat and tidy inside.
As stated my main issue was a couple of programmes which will only run on Windows (And have problems via Parallels) so have to be bootcamp, and my machine like many others would not install windows via bootcamp. (Its not known why yet, it has affected a lot of the nMP owners and Apple have not got a solution). so on that basis alone the nMP was a no go.
With the Lacklustre Performance in OSX, I am not sure it just felt sluggish at times, As stuff was on external USB Boxes I dont know if it was response times there, but there was just a sluggish feel to things I was not happy with.
Graphically, I felt the D700s a let down, I know there are issues in Mac mode not fully using both cards,
Price a minor one but I felt it cost a lot more than it was worth to me performance wise (This would not have mattered if the above items had not been an issue) but comes into play when there are issues, and when I built the Z800 that does recat and perform the way I want it to for just over £1000 compared to £4000 for the nMP which was not performing.
Not saying never, will keep an eye on developments in the future with the 7.1 etc but at the mo its WIN8 Big Box for me. (It fits my work needs) will not suit everyone. and the fact it also runs OSX nicely is a bonus although not something I will use in work environment but as a born tinkerer and with some bits on OSX I do love its a bonus...