Well, there's also the left over odor of smelly dirty socks which tends to put me off. First "popper" I ever tried was rammed up under my nose by a doctor (twice my age) who I was fucking in 1969. He had the drug store variety of breakable glass capsules wrapped in tight netting so when administering the stuff you wouldn't cut your fingers. Nope. It didn't enhance my experience at all, but I suppose the older guy was getting something out of it, because he continued to spasm in orgasmic heaven for a long time. And he left a giant load, as well.
Best to stay away from them. You don't have to be my age to suffer a drug-induced heart attack.