Ken Schwaber's comments in this scrumdevelopment thread are fantastic; we need to keep in mind that Scrum is a set of principles, not a call to follow a brainless list of processes.

I like something I heard Ken say during his course: Scrum is simple but very hard to do. Then he proceeded with an analogy to chess. We can all learn chess moves in a few hours, but mastery of the game takes a lot more.

So what does it take to be successful at a game like chess? I have some insight into this because much of my family plays chess, some even competitively.

1. Smart in the "right way": I don't think everyone can reach a high level like "master" in chess, even if they played their whole life.  You must be clever and a strategic thinker to do so. I consider myself to be fairly intelligent but I somehow can't seem to get past a certain level in chess--my brother, much to my chagrin, beats me consistently.
2. Experience: it's worthwhile to learn common "lines" in chess, which are basically patterns that show up frequently in high level play.
3. Courage and Bravery: to win you must think outside the box and risk in order to win. Overly conservative play will lead to stalemate.
4. Innovation: Creativity is a key to success. This is how good players beat computers.
5. A passion for the game: if you don't care you won't stick around to reach a high level of mastery.

I'm sure there are others keys for success.

The term "common sense" describes the light framework and principles of Scrum; however, it is difficult because it requires intelligence, bravery, passion, and innovation to succeed within the framework (as with most things worth doing).