I have a vest. I like it. Doesn't really affect the ventilation as it isn't 100% coverage. It is loose when uninflated, and has a big gap down the middle near the clips. Actually improves ventilation for me, because I leave it clipped up, but unzip the center of my aerostich in hot weather so I get a better breeze, since the vest will hold everything on should I crash. Doesn't cover up any vents in the roadcrafter, so win win.
Nothing doing with deflating it, you just wait 10 minutes.... or take it off. But I guess not everyone reads the manual?
I do unclip it on offroad sections where I need to stand, but nothing is perfect. Didn't want to have the subscription models with the auto crash sensors, just wanted to own it.
I've never tested it... As far as "might as well be in a car" you don't notice it on the road, and I guess I am more concerned with feeling stupid when I knew I could have had an air vest if something goes wrong, and less concerned with needing to reinforce a deficient sense of personal machismo.