5-Hour Energy

Okay, here's a question - has anyone else used it? I've only used it 3 times, but it seems to work really well for me (and Nat, I was wrong, it does have caffiene in it, apparently equal to one cup of coffee).

Does anyone know of any negative effects?

As crazy as it seems (and I was very skeptical for a long time) the stuff does seem to work as advertised, including the no crash part.