I remember driving to school that morning (I was in college at the time), and I could not figure out why there was only talking on the radio. I did not realize what happened until I got to school and looked at the TV. I could not believe it.
Now, 6 years later, I did not even think about it until someone from my office mentioned it, but on 9/11 this year, I was on a transatlantic flight to Madrid from ATL. Some people might not want to admit it, but the security in US airports is some of the best screening in the world (trust me, I have flown in to and out of many countries.
Many people might complain about the hassle of security, but for a (very) frequent flier, I really do not mind.