I've had oversized people spilling over into my seat, babies screaming in my ear, tedious-talkers rambling on, old ladies putting on nail polish poisoning me with toxic fumes, and it's miserable. To be fair, I also sat next to a very large man once and at first was not happy about it. But he somehow managed to keep all of his parts to himself for the entire flight and I could see he was very uncomfortable doing it. I was impressed. He clearly had compassion for those seated next to him.