I think a lot, if not all, of the items on the list are important, especially knowing the rules and remembering what the players are capable of.
Two things that I think a good DM needs, that arn't on the list, are flexibility and a sense of humor. Both are needed, because even if you sit down and think of 50 differnt ways that the PCs could respond to any given situation, the PCs will always come up with a 51st way. For instance, in a game I ran for my brother's group when they first started, I presented them with a gave, wooden wall made in the mouth of the cave, door in it, two arrow slits, and goblins behind it. The one response I didn't prepare for was the one the PCs actually did: the rogue unlocked the door, and the barbarian kicked it open, then proceded to use it as a bludgoning weapon to kill the unfortunate goblin standing behind it.
You just sort of have to let things go, and use the random wilderness encounter table to give the PCs something to do while you try to figure out how to recover the remains of the plot that they just shreaded.
That's also where the sense of humor comes in, you have to be able to laugh -- at yourself, and them.