I'm always a little baffled when people sacrifice their health for work - it's a very bad decision in the long term. You can always find another job, but once you damage your health, you may never get it back.
Modafinil could already be a modern alternative to coffee. It's definitely not perfect, but in some ways it's a lot better and it seems to be safe enough. It's far from perfect - for example I'm in the 10% who get headaches from it, so I prefer not to use it. But when a better alternative comes... I can't wait to replace caffeine.
I think, more interestingly, I'd ask if it were to become known that modafinil (or adderall) were harmful long term, would people still use it to gain competitive advantage. If we gain a nootropic with significant effects, at what point does it become disadvantageous not to jump on the mystery train? The 'line' that can be crossed is different for everyone.
When I looked at it from another perspective I changed my mind. It's irrational to not take something if the benefits exceed costs. If you can take something, with benefits that outweigh the side effects, why wouldn't you? Everything has costs and benefits. Of course most people will underestimate risk and overestimate benefits so you have to do this carefully.
Caffeine is a perfect example. When taken in proper dosage caffeine is beneficial with almost no side effects. The biggest side effect is addiction which isn't much of a problem with its availability and is easy to overcome.
Also, using caffeine pills instead of coffee and recommending them to others leads to wide eyes and "you take drugs?" kind of questions - apparently, that is crossing the line, yet drinking two huge mugs of coffee in a row isn't. Human psychology, go figure :-)...
My own experience with Modafinil is that it lets me focus intently on one or a handful of things for longer periods of time, but doesn't give me much if any boost in willpower to pick, so I rely on putting myself in the right environment where there's only a few options to pick from.
In fact, I don't, and precisely for this reason. Caffeine addictions seem to be just as bad to me.
Instead, I sleep more (enough so I don't have to use an alarm) and strive to cut unnecessary things from my life to save time. For example, I know it's a little cliche, but people survived without TV until 50 or 60 years ago. I got rid of my TV, and it saved me a lot of time.
(Note: dopamine reabsorption is also slowed by caffeine, which is why it improves your mood.)
My point is not to be pedantic, it's to say that no matter what you're ingesting, you're altering your mood. While I'd obviously agree that becoming addicted to mood-altering substances isn't a good thing, I think that (like sugar and fat) they can be used responsibly.
Adrafinil always needs disclaimers, but looks like it is now a thing of the past with Olmifon shutting down production.
The differences between coffee and modafinil are: coffee tastes better, modafinil does the same job for longer with less side effects.
In reply to your original comment - for work you don't care about, I'd agree with you, but plenty of people who do stuff like this, particularly I assume when it comes to HN readers, really do care about their work. For example there's plenty of times I'll work more hours than I technically have to because I want to, and so if I were to take drugs to help that, it wouldn't neccesarily be a case of "get a new job". Incidentally I do smoke, because I enjoy it more than I care about the health risks right now.
Or another, we can compare the effects of modafinil with getting into a car on a similar basis. With some basic knowledge of brain chemistry, claimed effects of the drug, understanding of placebo effect (~occurs in 1 in 3 or consider: drug OR Expectation/placebo Inferior to Drug AND Expectation), the drug's statistics, poor methodology in medical statistics and years of drug availability you can form a decent prior.
Based on my prior, taking modafinil is certainly not more lethal or less healthy than getting in a car and being near its fumes. So fear of health effects without any reasonable basis are not a rational argument to me. The supposed strong adverse effects? This is an argument for more understanding of how metabolisms and bodies differ, I have a confirmed strong allergy to nuts for example. Peanuts are much more dangerous to me than modafinil.
Yet I do not take modafinil. Not based on some unsubstantiated reverence for default biochemistry but instead on reasoned arguments. Its effects seem like they would impact creative thinking negatively. Furthermore, it is expensive and does not appear to have superior effects beyond being less addictive, a smoother delivery and a safer high dose cardiovascular profile than caffeine [1]. That is, modafinil does not appear to be any better at keeping you awake or focused than caffeine.
Similarly, I do not take caffeine because of its dependency forming nature and while it appears to boost working memory, enough studies indicate it antagonizes hippocampal function [2] to motivate me to minimize caffeine intake to every few weeks or less, as necessary. The mechanisms for modafinil are different so we can't expect all effects to be the same as caffeine. But it too seems to effect some improvement in working memory - most noticeable when the individual is lower performing [3] but according to [4] modafinil does show some negative effects on long term memory processes situated at the prefrontal cortex. in rats. Remember though, just because something appears in a medical journal doesn't make it true or accurate, especially when done on animal models or cell cultures. Nonetheless, the benefits in contrast with monetary costs and minute risks make modafinil not worth it and caffeine a very irregular thing for me.
Notice that I am not attacking your reluctance to take modafinil but rather, your opinion seems to be based on a nebulous definition of what a drug is and an assumption that the brain's architecture is optimal and any attempt to alter it will definitely be negative.
See also - Sulbutiamine. A vitamin B1 dimer.
[1] http://www.ncbi.nlm.nih.gov/pubmed/11862356
[2] http://www.ncbi.nlm.nih.gov/pubmed/19217915