For me it feels more uncomfortable than painful. When its torqued back, if you react and panic, it feels more painful than if you sort of detach yourself and think : "Okay, I'm in an armbar. Lets get out of it." Then just pop the leg and roll over.
Its one of the easiest subs to get out of IMO, but its also one of the scariest to be in. I suspect its more likely people tap from fear of danger than agony. I know I've never tapped until I was certain I couldn't get out of it, regardless of pain.
Sig courtesy of that photo-matic magician limba
I went out the way that I fight. I went out on my shield. Thatís it. Done. --Chuck Liddell
My goal is to end my opponent --Carlos Condit