I read Bruce Schneir's interview with Kip Hawley back in 2007, and came away with the belief that we have a team in place that has some significant knowledge of managing aviation security:

http://www.schneier.com/interview-hawley.html

As for what happened on Christmas, Bruce concisely describes a fairly common mantra about aviation security:

"Basically, there are three broad ways of defending airplanes: preventing bad people from getting on them (ID checks), preventing bad objects from getting on them (passenger screening, baggage screening), and preventing bad things from happening on them (reinforcing the cockpit door, sky marshals)."

And, with the exception of not getting millimeter-wave/back-scatter technology in place for full body scanning (which would have trivially caught the Christmas underwear bomber - and the lack of this technology at security checkpoints is perhaps the one real-failure of the TSA), I think the TSA has done an admirable job.

Note - one thing most people don't understand, is that by creating a rule which states "You must sit down in the last hour of flight" - the goal isn't to prevent mad-bombers from standing up, it's to make it very clear which ones the mad bombers are for the Sky Marshals and Airline crew - it's for a week, and the rule (hopefully) is given a pass for those who clearly need to go to the washroom, need a blanket, etc...