They say that Grivory is the same as Zytel but with more glass content to stiffen it further.
We just got one of these guys in at the shop a couple weeks ago and I must say that I'm impressed. I honestly feel that it would make a good folding field knife, as the blade is durable, the triad lock should prove stronger than a standard back lock, and the ergos are fantastic. As long as you were belts, the weight isn't horribly noticeable in the pocket. Noticeable, yes, but not horribly so.
That being said, I agree with all above in that it would probably be better to use a fixed blade for anything that the Rajah would do better with than a smaller folder. They'll have it for a while though. It's not horrendously priced (unlike a lot of their stuff) and it's different enough to grab peoples attention.