I smoke, and I did a little research on these things. I don't trust 'em. Sure, they eliminate the tar and whatnot, but they actually input a safety feature on a lot of these e-cigs because there is a danger of nicotine poisoning if you smoke it too much. I also don't entirely trust breathing vapor into my lungs (I know, I know, I already breathe in tar, so who am I to talk?). There are probably side-effects not yet discovered that are in fact worse than smoking.
A co-worker gave me a sample e-cig for Christmas as well, and I tried it out. Not bad for a quick fix, but they don't taste that great, you have to suck it like you're drinking a milkshake, and I got cotton mouth from it. I'll stick to my regular cancer sticks.