The main interest in the 9/11 commision report (downloads here) is whether or not it will help John Kerry beat Bush in the upcoming elections, but it's no wonder that CNN isn't leading with the political story but with the real life drama of the passengers who fought back.
It's a dramatic story and shows what an absolute nightmare september 11 was on board that plane. Once the passengers attacked the hijackers, the hijackers started to roll the plane first and when that proved inefficent abruptly diving and climbing. The cabin must have been a complete mess. Furthermore - the pilots actually received a warning before the hijackers attacked the cockpit, it was just such an unexpected warning that the pilots asked for confirmation. A lot could have been different with locked, steel reinforced cockpit doors and with the warning being taken seriously. But at the time, the content of the warning was just too unimaginable to be accepted at face value without double checking.
What is a little harder to estimate is the political dynamite. Danish newspapers carried a list of some 10 early indications that something was afoot where the same names cropped up again and again, but I have to say that I believe very much that this is one of thoses cases with 20/20 hindsight. I have no idea how many names and people the CIA, FBI, and NSA combined are trying to keep taps on, but it must be thousands.
It's no simple task to make sure that all the information about any specific person or name gets collated and accumulated in one place, and once it does you have to recognize what level of threat there is.
Secondly, let's assume the engineering effort of large scale monitoring of intelligence targets can be solved, then there is the matter of public oversight. It's not a very pleasing alternative to have >100K staff controlloing the whereabouts of millions of people on a daily basis. There has to be balance as well.