Just received the newsletter and so the Gamezebo article. A very interesting reading, it's good to realize sometimes that there is a huge amount of work behind each game.
Also, it's true, mapping is fundamental. Without good and entertaining maps, the game is only mediocre, no matter how good the other "ingredients" are. I must add, though, that Indi was always pretty good in creating maps. Even the very first game, LP1, had pretty decent maps. Especially all these little secrets (coins in barrels, jokes, party banters when exploring) help making the game more entertaining.