If there's a universal thing to derive from this great article, it's:
"The point is, most of these ideas are simple and obvious in hindsight, but I had to make a lot of mistakes to find them. It's nearly impossible to coalesce good design decisions straight from the ether. The only reliable method is iteration and trial and error."
Still, my productivity increased when I consciously forced myself, when faced with some difficulties where I have failed once or twice, to resist writing more code, switch down the PC, go for a walk and think (or a good bath). Thinking hard for a few hours about a problem is underrated IMO.
I'd also add "no aspect of a game (or other piece of software) exists in a vacuum." 90% of the changes to the camera control were directly linked with changes to gameplay and user interface, which were only arrived at by iterating on the game as a whole rather than just the camera aspect. The whole article would have worked just as well if it were titled "How To Make A Game Fun".
"The point is, most of these ideas are simple and obvious in hindsight, but I had to make a lot of mistakes to find them. It's nearly impossible to coalesce good design decisions straight from the ether. The only reliable method is iteration and trial and error."