I've got a hit-air jacket and love it! I've had mine about three years or so by now.
I understand that $500 is a lot, but one can easily spend that much on other top name riding gear. I've also heard the comment before, of, "Yeah, it's great, but it doesn't always work." (like on a low side where you're not thrown from the bike). 1) it's designed to work when you are thrown from the bike, 2) if you are in an accident where you're not thrown from the bike, then you have just as much protection as you would from any other motorcycle jacket with armor, and nothing's lost, 3) I don't see why it wouldn't work if you are thrown from the bike (these jackets have been around in Japan and Europe for over 10 years, I trust they have worked out the kinks and have a reliable system).
From what I recall reading, one of the leading injuries in fatal motorcycle crashes are broken ribs puncturing the lungs or heart. The Hit-Air products will protect your ribs (along with your neck and tailbone). The vest/jacket is fully inflated in a 1/4 of a second, and partially inflated enough to provide some additional protection of the air bag in even less time. For me and my safety, it's a no-brainer, what is my life worth? If I spend $300 on a quality jacket with no airbag, and I get in some serious accident and require hospitalization that could have been prevented by spending an extra $200 (which is less than an ambulance ride if I'm not mistaken), then I'll go for it. I understand the airbag jacket isn't for everyone, just trying to provide my argument for why it's a good investment for me.
I'm sorry if I sound a little ranty this morning. I'm just a firm believer in this product (not an employee or anyone else with financial interest), and I think that the argument of "it doesn't always work" is mis-informed. I understand the cost part of it too, that's why I don't have a summer jacket (well that and I live in SF, where my heater has come on every morning for the past week). Check out some of the videos they have on their website and youtube. http://safermoto.com/