By way of Borepath's blog, a nice representation of the rate of return the public has experienced on its investment of insane amounts of time, money, and humiliation into the TSA organization since 9/11.
There was one significant security improvement made after 9/11---in fact it was made on 9/11.
It was that the public changed its expectation regarding the impact of a hijacking from 'we'll take an unscheduled vacation to Cuba and pick up some cigars' to 'some SOB wants to turn us into charcoal by using our plane as a guided missile'. Changing the expectation is all that it took to make such behavior impractical. All of the rest is theatre---expensive, humiliating, and time-consuming theatre. All of the terrorist incidents that have been thwarted recently have been done so by...you guessed it...passengers, or, if you prefer, by the unorganized militia of the US. Not for nothing did Sun Tzu say, if you put your men on deadly ground (i.e., ground where it is clear that you must fight and/or die, retreat is obviously impossible) they will live (because most of the slaughter in ancients battles came after one side's morale had broken, and those 'on deadly ground' tend to have very strong morale). Because the public now recognizes a hijacking as 'deadly ground', it is extremely unlikely that we'll see a successful repeat of the tactic.
But the TSA is good for one thing. It is good for increasing the anger of the population against the system. Check out the comments on any site with stories about the TSA that allows open comment. Also check out the up/down votes by other readers on said comments. It strikes me as not unlikely that the tipping point on the campaign to delegitimize the judiciary will come when someone decks a TSA agent for inappropriate action and the case goes to a jury trial where the jury plays the nullification card. Every nullification makes the next one easier. Perhaps the TSA will turn out to have been worth the price all along.