I have written a write up review of my helite that I've been using for about three years, if you search. Never gone while disembarking, so that's not an issue.
I agree, gyro sensors will be better overall than a lanyard, but it also has cost implications. (The reaction is likely to be swifter.) I have two experienced friends who also use them and are happy with it.
I don't know whether I would buy another, as I no longer commute on the bike, but having said that, I'd rather have it than not, on balance. It's the same price as a decent lid, and may reduce the severity of injury. I buy decent gear and wear it all the time. I appreciate that others don't, and don't blame them. I've crashed twice, both at speed, and both my own fault. Probably, the vest wouldn't have helped in either, but then again, I don't get to chose my accidents.
Also, I seriously disagree with Geoff's take on the matter (sorry, boss!) But the cost is a fraction of what you've wasted over the years, and let's just say it minimises an injury a little, at that time I'm sure you'd say you'd have been happy to spend three times as much! Indeed, I would also argue that not much will help you at 200mph, but at 40mph, they probably will.
The odds of being hit by lightning in the uk is 1:1.2million. The likelihood of being involved in a bike accident is significantly higher. Otherwise, you'd not bother using any gear at all, a position I don't think Geoff is arguing for. (I also appreciate that it was tongue in cheek, but it is important to accurately assess probability.)