I only take this drug for "emergencies." Like if I've had no sleep, and have to drive for long periods of time. Or staying awake in class. Or when I've had no sleep, and have to work 12 hr shifts at night. It will definitely perk you up, makes you feel alert and productive. HOWEVER, it CAN suppress your immune system. The package insert even lists "fevers, flu-like symptoms, and cold sores" as a side effect -- that's because your immune defenses are down, either from lack of sleep, or a direct effect on the immune system itself. Just because you feel awake doesn't mean your body doesn't need rest. The downside is that you can't fall asleep, your body KNOWS you haven't slept, and you feel like complete crap when the drug wears off, and it can trigger a flare from overexertion. It also makes me nauseated about 10-12 hrs after I've taken the drug. (Every time, like clockwork.) It kills your appetite, which some people see as a plus, but when you lack nutrition, you will feel ill. It ALWAYS gives me a fever, not sure if it's from the effects on my immune system, or from the overstimulation of the thyroid. I've also had major drug interactions with it. So if I ever feel I NEED to stay awake and caffeine just won't cut it, then I will take half a tab (100mg) with a full meal. Make sure you check the side effects because they're common. And it can be addictive -- in lab studies, monkeys preferred Provigil over cocaine! That always freaked me out a little.
http://www.drugs.com/sfx/provigil-side-effects.html
http://www.askapatient.com/viewrating.asp?drug=20717&name=PROVIGIL
Not something I could take every day! But everyone's different, so of course, follow your gut and your doctor's recommendations. It can be a miracle drug for many people, I just wasn't one of them!