I haven't tried a ZX2, but I can tell you my experience with the M20.
The bad:
1. Weight transfer is pretty much nonexistent.
2. Slight loss of top end
3. Takes constant messing around with the air pressure to keep it dialed in
The good:
1. Once you figure out how to keep the air pressure adjusted properly to your weight and riding conditions, the ride is incredible
2. Virtually indestructible (at least in my experience)
Overall, I will gladly take the speed and dead stop acceleration losses to have a suspension that is infinitely adjustable at the flick of a switch. If you get one, make sure to get the diamond option... having to mess around with a hand pump all of the time would be a huge PITA.