So I'm thinking of swapping my Spinergy RevX's with a guy at work. He has Mavic CXP 21's. Even/good trade?

Your loss is your gain....you decide. You're giving up a much more expensive wheelset for an OEM wheelset. But in the longrun, you'll still have a decent wheelset while the guy with your Rex-X's, he may or may not have a functioning set of wheels. Hope you weren't intending on touring with those Rev-X's.