After reading several opinions and the review, I believe that is an outstanding add-on, nevertheless, an aircraft like that, deserves a good FMS. When I say “good”, I mean “really good”, including VNAV capability.
As a real life ATPL, I cannot imagine such a machine flying VOR to VOR. It doesn't make sense (for me, of course).
I also have FSX and I wouldn't have PMDG B738/9 NGX, if it hadn't a good FMC.
If that improvement occurs, I'll buy the Challenger 300 immediately.