First she was quite poised and I'll give her credit for being quite effective as a witness.
I think this testimony does not refute the idea that terrorism was not a top priority for the Bush administration. She consistently argued that they were taking a strategic and not a tactical approach on several different fronts, however a strategic approach does not mean that an item is a high priority. It is quite obvious that this strategic approach was not deemed as important as missile defense or even Iraq pre-9/11. It is all well and good to say that they couldn't have made the domestic structural/strategic changes in 238 days, but they didn't make substantial efforts to get started on these changes. She say much of anything to indicate that if the attack took place on 9/11/02 it would have been prevented. The Clinton administration also failed to make these key strategic changes, and can rightly be critiqued for failing to make them.
Secondly, adopting a strategic approach involves a turn-around time, particularly when the strategic approach is not given priority. Until the problems are fixed, steps must be taken to work around them until the corrections are made. These steps will be imperfect and are not guaranteed to work, but if they are not taken, you are left blind in the interim. Thirty three times the principles government figures meant on various issues but not on terrorism (number quoted in the session, wasn't challenged). This was a changed from the Clinton Administration where the principles did meet. Had such meetings occurred there is a chance any of the multiple clues regarding the attacks might have come to light. Alternately someone may have noticed that the FBI apparently completely ignored instructions (as was stated in the hearings without disagreement) to concentrate on Al Qeada sleeper cells and potential attacks. Rice, by her own initiative, should have been more active in making sure these steps were taken. Alternately, the top terrorism official, Richard Clarke, should have been given the authority he had under the Clinton administration to take these steps himself.
Mistakes happen. A Gore administration may have made similar mistakes or may have made entirely different ones that had the same results. If the Gore National Security Advisor had made similar mistakes, I hope I'd be similarly hard on him or her.
National Security Adviser Rice is flat wrong in thinking she did enough to prevent 9/11 and if she actually believes what she's saying than she should be replaced. If this reflects her general approach, than her lack of imagination and belief that large scale changes can be taken without steps in the interim demands that she be replaced as National Security Advisor.