I ordered my nMP on launch day and finally received it in early February. It was to replace another first generation product - the Mac Pro 1,1 that I'd purchased back in 2007 and had served me very well. I'm still as happy as a pig in brown stuff with my cylindrical masterpiece. I remember one day soon after buying it wondering what the whirring sound was in my room only to realise that the hands of the clock on the wall above my nMP was making the noise while my computer was completely silent.
The lack of internal storage has been an issue, but not one I haven't coped with. If costs had been lower, I'd have liked a Thunderbolt storage array, but instead I went with a Synology NAS which has been marvellous (and offered me all sorts of extras that have streamlined my workflow and made working away from my home office a breeze - just access the NAS via WebDav on my MacBook Pro and away I go).
You can imagine just how much faster the machine is over my MP 1,1, but it's not just the speed increase - everything about this machine is a massive step forward for me and worth every penny.
In summary - still very happy with the machine. The prices of IPS based 4K monitors are dropping rapidly at the moment so I suspect during Q1 or Q2 2015 I'll be buying a 4K monitor to replace my 30" ACD and then my new set up will be complete.
The nMP was a long time coming, but I for one am very very happy with it.