Not a controlled demolition. Conclusively disproven by many professional engineers using not only the same eyewitness accounts, but also expert opinions, analysis and computer simulations to show that everything associated with WTC could be accounted for by a high speed impact followed by an uncontrolled fire. Its completely stupid to plan a controlled demolition and use an aircraft impact + fire as a cover when the aircraft impact + fire could do it alone.
Ignored warnings? No doubt in my mind. They ignored the FBI agent who warned that terrorists were getting suspicious flight training. I also have no doubt that the Mossad knew about 9/11 and likely informed the White House. Mossad agents were seen watching the WTC, an Israeli shipping company broke its lease to move out of the WTC, and there was the huge spike in put options on the airlines that were to be hijacked. Definitely not a 'surprise attack'.
Now, whether they deliberately allowed it to happen, or it was 'just' gross negligence, I don't know. Allowing the attack to occur certainly fit in with many of Bush's goals.