Security lines are moving more rapidly because travelers are more experienced in dealing with getting through airport security and now unprompted empty their pockets, take off their shoes, pull their computers out of their bags, and pull out their carry-on liquids in clear plastic bags. Speed is also better because screeners have become more experienced in identifying and dealing with things that deserve additional attention as they go through X-ray.
Ultimately the quickest way for travelers to pass through airport security checkpoints may be by having them go through scanners that see through passengers' clothes. The TSA (Transportation Security Administration) is already using such scanners on a limited basis and is quickly rolling out additional machines to major airports across the country.
Passengers are currently required to stand in a booth with their arms raised to go through such scanners. Eventually it is hoped that travelers will be able to simply walk through such scanners making the security process that much faster. These scanners have been in operation for some time in Europe with very few issues, thus the process has been tested and will most likely be very well received here as well. The number one priority for travelers is safety, and they are willing to go through such inconveniences to insure their trip will be safe.
Airport security is further being tightened by employing security agents with psychological training to observe travelers more closely and identify people whose behavior suggests additional screening is warranted. It is unclear how this will be accepted, and if in fact it is effective. This too has been tested in Europe, with very good results.