I'm not kidding...get two or three rockstars, and sleep will be borderline physically impossible. I stayed up for 72 hours finishing a project for a final exam a couple years ago in college, and I don't think i would have lasted 48 without this stuff.
Edit: Situations like this is the exact reason I'd like to see modafinil/Provigil/Alertec available over the counter
It seems like it would be so much healthier to take a more targeted anti-drowsiness pill than suck down all that caffiene and sugar. But alas....