I'm fairly comfortable with the course my life has taken, so I'd find it hard to swap lives with someone that I know very little about, no matter how they look or what their abilities are. I also wouldn't want to have to hand my life over to someone else, either. Sure, there's nothing I can complain about in my current situation, but it'd be easy for another person to pick out the parts they hate about it (and I'm sure there'd be quite a few).
Being able to switch lives with someone that I'm a more familiar with is a little bit more enticing, though. Still, I don't think I know of anyone that has a substantially better life than I do, so even then, I probably wouldn't switch if given the opportunity.