I like visiting other countries where the metric system is used. It's quaint. It makes me feel all cultured and well-travelled and stuff. Great idea for attracting tourists. It's almost like a natural wonder; except anyone can have it.
As a traveller it is kind of like roughing it in the woods. There's a certain challenge to figuring out exactly how big, deep or fast. All in all its part of the experience of being away from home.
On the other hand, at home I like the english system. I mean, almost everyone has a foot or two. It's easy to understand. And then there's the inch. Inch-worms are about an inch long. Also easy to understand. A yard? Why, that's three feet. You do have friends, don't you. Borrow a foot or two. Speeds and weights are just as easy.
So if you are handicaped or friendless or not good at english I would suggest using the metric system. If you are currently using the metric system: get some help! There are many organizations dedicated to helping those less fortunate than americans.