I've been experimenting with the anti-sleepiness drug Provigil for the last few months, long enough to have reached some conclusions. [Caveat: I'm a Diet Coke fanatic. I drink it all day long; I have at least a 6-can-a-day habit. I feel groggy on days when I drink less than that. So there's always a pretty high background level of caffeine in my system.]
The great news about Provigil is: it really, really works for the purpose it was designed for. If I happen to stay up very late some night and I need to be awake and alert the next morning, taking a Provigil in the morning gives me that ability. I can be wide awake and productive at work on just a few hours of sleep, when I need to.
However - contrary to the hype - it does not make sleep optional or all-nighters particularly easy and productive. At least it doesn't seem to do so for caffeine-addled me. I tend to find I am unusually tired in the evening on days when I had to take Provigil in the morning. It feels like it resets my sleep clock. Like changing time zones, it adjusts my metabolism so "wide awake" comes earlier than it otherwise would, but "tired and ready to sleep" is likewise brought in a few hours ahead of schedule. And it doesn't entirely remove the "sleep deficit" effect although it does reduce it a bit; my body wants to sleep a bit more to make up for sleeping less earlier.
Also, the Provigil doesn't help me get out of bed. Once I manage to drag myself up, take a shower, down a pill, I'll feel awake. But the dragging-myself-out-of-bed part is still pretty hard, and the less sleep I've had the harder it is.
I take a single 200 mg pill in the morning on days when I find I've had less than 6 hours of sleep and really need to be alert at work. On days that don't meet those criteria I don't take the pill, and I don't miss it. I never feel jittery or have difficulty sleeping due to it, I merely feel awake at the times I need to.
I use the drug a couple times a week. My initial prescription of 30 pills is getting low; I plan to get it refilled. It is very nice to have this tool at my disposal. Like aspirin, imodium, and throat lozenges, it's just something I want to have handy in the medicine cabinet or by the bedside. Not to take all the time, but to use when in need.
Provigil: It does a body good. :-)