I have an Air2... I like it a lot. I've done maybe twenty minutes on it as my primary, having handed off my main second-stage to a buddy. Perfectly comfortable. Love reducing hoses.
Two warnings though:
1) I think the standard hose for it is a bit flimsy, and the apparatus seems to be prone to 'catching' on other gear. I recommend adding 4 thin zip ties, i.e., doubling up on zip ties.
2) The internal metal connectors do not seem to be coated against rust, so either do so yourself, or rinse your gear *very* thoroughly all the time (or both).
Also, be aware that it has a non-standard connector, so if it blows out and you are somewhere remote, you are out of luck (this just happened to me).
There is a DiveAlert for this size connector, though, which is good.
Lastly, and this is sorta subtle, but I've noticed that the increased weight on the left side (Air2 and DiveAlert), combined with the lack of the weight of a standard octupus on the right, actually tilts me a bit. I counter-balance by loading my other stuff (e.g., knife, safety sausage, etc.) on the right, but I've also been playing around with how I set my weights.