Modafinil can (sometimes literally) save your life when you're sleep deprived or during a crunch time. Not to be abused, obviously. Everything else just fails in at least one of 3 ways: tolerance build up, side effects or just not enough impact.
Something I've noticed with it is that I can breath a lot easier when I take it. I have asthma and get seasonal allergies, and it dilates my sinus cavity.
Like any stim, especially in our community, be careful.
It sure is fun, but pretty much wasted if doing on a day to day job.