Interesting. I take modafinil 2-ish times a week, sometimes to skip a night's sleep to work on my own projects, sometimes to get a really productive day at my day-job with a startup.
My subjective experience with driving on Modafinil is very different: I become significantly more aware of everything on the road. It turns me into a laser, sure, but a laser that's constantly scanning back and forth. Too many confounding factors to say why that is.
I haven't noticed any diminishing of 'broad thinking'. Not sure I could claim any increase, though.
His claim that it's better to get productive days through other means seems to be a false dichotomy: Modafinil isn't dangerous like he's convinced it is, and while you can get productive through better health and rest, you can get even more productive by eating healthy, exercising, resting properly, and taking Modafinil. It's not clear why he thinks that Modafinil will force you to be unhealthy, thus making it a choice between "healthy" and "moda" (Honestly, the days when I take Modafinil, I find I have the focus to exercise harder and longer, and the willpower to eat much healthier).
His points about 'shortcut to a really productive day', 'having a clear big task to focus on', and 'drink a lot of water' are all spot-on, though.
I have to disagree with his recommendations: I think Modafinil's value proposition is positive for almost everyone, and proportionally more valuable as the value of your time or focus increases. HN readers in particular tend to have valuable time and extremely valuable focus; Modafinil is a huge gain, something like a large fraction of just the positives of amphetamines, with the negatives of caffeine instead.
The illustrious gwern has an article covering the medical research, benefits, risks, a novel cost/benefit analysis, and supplier information here: http://www.gwern.net/Modafinil
(Yes, it's been linked a few times already in this discussion. Go read it already.)