I have to admit that I know precious little about this, but it’s supposed to be along the lines of Nvidia’s computational cards right?
Will it be supported by VRay?
people already posted on this forum about it. Short answer is I think they are working on supporting it. 
Heya
Yea Xeon PHI is CPU on ur PCI, the 5100 version has 60 cores and each cores is HT x4, so 60 cores, 240 threads.
Regarding speed last I read 1 Xeon PHI card = up to 2.5-3x speed of 16 core Xeons.
How it translates to price…
16 core xeon = £5k - custom build, from BOXX = around 10K
1 Phi card = 1.8k
Topic, http://www.chaosgroup.com/forums/vbulletin/showthread.php?70608-Xeon-PHI-amp-Vray
They are porting Vray to Phi bit by bit or so.
Lovely, didn’t see the other topic - my laziness is to fault, sorry. These are some pretty exciting times for rendering, with the likes of Nvidia putting out the titan and intel doing this.