[rue]

That's correct, I used “stimulants” in the narrow sense and should have been clearer.

I don't have much information on modafinil or other substances in its class so I can't speak to it except to say that the early studies seem promising (I say this as someone who really, really hates the waste of time that is a good night's sleep) despite some reported side-effects.

I would certainly like to see more studies, as well as further information about sustainability. That is, it's great if it really does let you work reasonably well for 3-4 days (within 30% for < 2 days isn't really conclusive), but even then there's the question of what happens after. I doubt you'd just be able to sleep 8 hours and get right back on track.