I've gotten pepper spray in my eyes a few times when it sprayed back at me after i just juiced somebody. It stings, yeah.
Every time i've used it that stuff has kicked butt.
A CS grenade is like a solid cloud of thick white gas. MUCH nastier than the gas chamber they make all the troops go through. It's effects are greatly amplified by the thick white cloud. You run into all kinds of stuff because you can't see doo-doo.