I wear a full knight's armour when I'm chainsawing....
...that way I can stand under trees when I'm felling them so that they don't hurt the grass they land on.
Seriously, the only saws I have with chain-brakes are baby Stihls and yes, I use them. It's extra insurance up a tree to click the brake on when I start the saws and not have a spinning chain, or down at the river, where I put the brake on while walking between washed-up logs instead of turning the saw off.
My big saws don't have chain-brakes, but I may have to find some because OSHA regulations here mean that I can't get access into many areas due to not having chain-brakes on my saws.
Although I haven't been injured by a chainsaw, I had several near misses with a Pioneer 3270. Not quite sure why, but I got the feeling the saw just didn't like me, so I sold the cantankerous thing. My other saws have only kicked back when I've done something particularly stupid like saw up branches on a pile of sawn rounds - almost guaranteed to snatch!:greenchainsaw: