The air shock on the HP2 E wasn't all bad and significantly better then the G650X application for certain. I've yet to simulate the traction I could get with an air shock in slow moving technical riding with any aftermarket shock, but the predictability of a hydro shock in the rear is way better then the air shock when at speed.
The biggest problem with the air shock, particularly on the G650X was when people would use it as a ride height adjuster, that's what lead to 90% of the G650X failures I saw and of the HP2 E failures (which was minimal) they were all used in extreme conditions either loaded up or racing and in my opinion outside of the designed parameters. The biggest problem is getting the Conti shock repaired should it ever fail and it is made of rubber and relies on rubber O-rings for it's integrity,...they will wear out.
Just some dude on the internet,..