I guess it ultimately boils down to control.. Now you no longer just jump in the direction you moved before but can actively change it. You can go round tight corners, you can stop yourself (model

) from falling down in spacemaps after being pushed of. Play NexFace and get hit on top of the tower with a nex. In 1.5 you would have just fallen into the void. Now you can still hit the ground. You can better correct your flight path, you can use the aircontrol to gain speed. Now Nexuiz feels like being inside the level, being part of it, not just jumping through it. I guess people familiar with quake1/qw/cpma will love the new air control as its similar. Except for the missing strafe jumps that is.
I was testing a quake4 map yesterday and jumping through it felt soo limited.. I know you can do almost the same with crouchsliding but thats on the ground. Yeah some people like this new control and some do not. Thats taste, but i think it fits Nexuiz fastpaced style much better now. Fast and in control!