Both my wife and I wear Point 2 airvests and have done so for about four years. I originally bought one for her for horse riding, and some months later she was unseated when the horse bolted, thrown high in the air and landed on her head. She suffered 3 fractured vertebrae in her neck, 1 on her spine and 2 compound and compressed fractures on both wrists, but before any suggestion is made that the air vest didn't protect her because she suffered heavy injuries, the hospital surmised that the inflated vest stabilised her neck minimising further damage or possible paralysis.
My daughter wears one and has been thrown several times by idiot horses (can you tell I'm not a fan?) and suffered no injuries.
Bottom line is that we won't ride without them, even on our Mediterranean tours where temps can reach 50C., and TBH I don't feel any weight from the vest when I ride and accept any additional heat from wearing it in the same way as wearing the rest of my riding gear. The one and only time we didn't the bike went sideways big time on a wet road in a sudden downpour and frightened the life out of my wife, since then they've become a permanent fixture.
I sometimes look at the scooter riders in Greece who sport flipflops, T shirt and shorts and envy them their freedom, but I think I'll stay ATGATT !
As an aside I was also a former Police Traffic Motorcyclist and in the course of my duties have attended many collisions, both fatal and serious, and would always encourage airvests for any rider. Anything that may minimise injuries has to be seriously considered, but at the end of the day it's a personal choice... after my wife's accident it was an easy choice for us to make.

This is the only photo that I have of me with the airvest, absolute rubbish I know... I'm not praying, I'm securing straps on a Greek ferry. But then again, if it's good enough for Valentino Rossi then it's good enough for me! I figured that if I'm wearing the vest I may as well get a hi-viz one.