Never been in one. Never will.
About a year ago, I was the only person in my social group to be in a serious relationship. Now, I'm the only person to not be in a serious relationship. I think it can be easy to forget the flaws of being in the opposite state while in a relationship or single, but I think the problem is especially prevalent while single. Looking back, and realising how crap it sometimes was, sort of makes me wonder whether I'm better off single. But, shit, maybe I'm deluding myself.
I've never experienced the desire or drive to seek out a relationship, so I wouldn't know. I'm pretty content as I am, though.