I'm not sure its an improvement on security, but certainly it won't decrease it: remove the interrogation faced by international pax coming into the US. Since it isn't carried out on any internal N American flights (including US/Canada), it's window dressing.

A lot of the security things within the US I personally think are down to poor equipment selection, which the screeners on the ground have little control over.

And yes, I'm a frequent flyer who knows the drill, but can't remember what all the differences between airports (especially US/European), so maybe more signs earlier warning me what it is I am to do will stop people yelling at me? To someone who travels in the US only infrequently, I feel that there is a great deal of assumption that I will know what the current rules are - yet strangely, I don't spend my time trying to find them out