Well it's smoking, so it's not 70% healthy, it's 0% healthy. Let's not kid ourselves.
That being said, I do enjoy a good shisha from time to time. :) I've unfortunately only been to a hookah bar once, as my girlfriend hates anything having to do with smoking, but it was a great experience. Easier than smoking a cigar, and just as enjoyable. And hookah smoking, like cigar smoking, usually isn't an addiction, so it's not going to be as bad for you as smoking a pack or three a day if you only do it once in a while. It's a great way to spend an evening with good food, good friends, and some good stimulating conversation.