I wonder why they chose to use Intel NUC for this. It has dire price/performance. I built a cluster (see http://rwmj.wordpress.com/?s=cluster) recently, and I used AMD hardware for it because (as of right now) the performance is unbeatable for the price. I have a 32 core cluster that cost me £1300 including everything except a metal box to put it in.
That's pretty cool. One of the goals for the orangebox was being robust and compact enough to throw in a suitcase and fly to a conference. The nucs win on compactness, and also via intel's vpro/amt can do remote power management (ie. ipmi light).
Nice -- didn't know that Intel now had a serious remote management offering. These AMD mobos do wake-on-LAN, and that's it. They don't even have serial BIOS.
To be honest, Intel's AMT is a bit of a PITA, but the Orange Boxes were assembled to have some resemblance to real racks of hardware. So remote out of band power control is essential.
There's something quite magical about using Juju and MAAS on the Orange Boxes and seeing the LEDs light up as you scale out a service (e.g. juju add-unit -n 5 nova-compute).
Every single Supermicro and Tyan board I've ever used. Also every Dell, HP, and Sun/Oracle server I've ever used (though those can be a bit more of a pain). Really, anything with a halfway-decent IPMI implementation.
Portability; from looking at your site you're using a standard ATX motherboard. The Orange Box is for demoing MAAS/OpenStack and needs to be portable enough to go on a plane.
Cool cluster btw, it'd be neat to see you blog about using MAAS on it.