I am often asked what is the coolest new thing in firearms technology...and the answer isn't anything having to do with the actual gun design. Our guns today are mechanically the same as they were in 1950. What has improved markedly are materials and optics. A Glock is just another simplified Browning tilting-barrel action, but its polymer frame makes it substantially lighter and cheaper, and an optic on top makes it substantially more effective.
We have had optics on competition handguns for a while now, but those rigs have never been practical for daily carry. The optics were bulky and often a bit unreliable, and the mounts were also bulky and inefficient.
IMO, the most substantive change in recent arms technology is the synthesis of a light polymer handgun with an optic that is durable, reliable, and small enough for practical daily carry. One of the longest-working advocates of this system has been Gabe Suarez, so when I wanted to try out the leading edge in carry guns, I went to him.
The setup I have been using is a Glock 19 (3rd generation, although that doesn't really matter) coupled with a Trijicon RM02 optic and a Glock slide made by Suarez, and carried in an appendix holster with a guard for the optic. Over several months of practice, training, and competition, I have found it to be an excellent sidearm. The co-witnessed iron sights allow me to get on target just as fast as with no optic, while the dot allows faster transitions between targets, much better shooting from awkward positions, and more precise shooting at long range and on small targets.
For lots more commentary on the concept, check out Suarez' page of articles and such: