I can't speak as to why the Nitrous Cams were discontinued, but I have spent time behind the string with the Nitrous Cams and the furious cams. They are different cams and both have their own pros and cons. I personally have enjoyed shooting the B base nitrous cams the most of any cam I have shot. Having said that, when you are shooting full FITAs or 28 target field rounds, the draw cycle of the nitrous cam is not ideal. The smooth draw force curve of the furious cam does fit quite well though. I have not had any experience withthe fury cam, so I can't relate to the speculation that the furious cam is a hybrid of the Fury and nitrous cams.
I have also played with an S4 with Tru Arc cams. That was a great feeling set up. The tru arc cam has also went the way of the dodo bird.
Fortunately, the folks at Martin are keeping with advances in technology and listening to shooters. They always seem to be in the forefront, but I imagine that if the demand for Nitrous cams remains after another year or two that they may consider bringing them back...not certain, but it makes sense to me.
As for the cat cams, they are a quick cam, definate wall with the draw stop and easy to play with. Definately a good cam system, but needs something to accomodate short draw archers so they can hop up speeds for 3D or push heavier hunting arrows at the same speed.