Electronic Cigarettes

Has anybody ever used those electronic cigarettes?  I saw a group of teenagers using them and wondered about them so I'm looking for a electronic cigarette faq page.  Are they better for your health than regular cigarettes?  How are they cost-wise in comparison to the high cost of a pack of cigarettes?  Do they give you ashtray breath like cigarettes do?

I don't actually smoke (anymore) but with teenagers using them, I wondered.