I agree. I think the original article is mostly right and very insightful. But what I've discovered over the last few years is that sometimes maximising productivity requires knowing when to take a break from the problem. A lot of time I'll spend an hour trying to work on something, hit an obstacle, try to push on it a bit, realise that it's hard, then just take a break from it until I have better inspiration on how to deal with it. Then a week or month later, once the idea for a solution has crystalised, then I can do a big push and get it done.
Also, just walking around thinking is the most productive time of my day.
The reason walking around is a good source of ideas is basically mindfulness/Zen/whatever you want to call it - put your brain in a bath of non-problem stimuli and stop verbalising your thoughts, and you can actually hear your brain generating new ideas. Of course it doesn't mean you'll get something useful straight away, or even in an hour, but you'll get new spontaneous thoughts and that's a good start.
This is why, when you do take a break, it is essential not to occupy your "doing" mind - by reading HN/twitter or playing Skyrim, my weaknesses - and just relax.
Also, just walking around thinking is the most productive time of my day.