I always read his blog. Even if you agree or not with him, this man is doing great from the educational point of view, I feel I'm learning a lot from his reading. There are not so many developers writing theirs ideas so openly.
Some nice thing digged from last article:http://www.raphkoster.com/2006/07/18/use-based-systems/
"A fun little story for those who think SWG was still too grindy: three
days before the game launched, the designer in charge of advancement
rates went through them and made them all ten times slower. His concern
was that players would max out the game in a matter of weeks, and then
quit. This actually hit the live beta servers, and I reverted it back
out as soon as I saw how excruciatingly slow it was: making literally
thousands of blaster bolts to advance one skill box. I felt that I’d
rather people exit the game having had fun, than stay and not have fun,
or quit because it was too grindy."