Can someone explain to me what this new LDA trigger is all about?
LDA means "light double action." Basically, it allows you to carry a 1911 with the hammer down. It has a pivoting trigger like you find on double action pistols instead of the sliding (straight back) trigger found on traditional single action 1911s. The trigger has to move through a long arc, which draws the hammer back and then releases the sear to fire the gun. Of course, in a traditional 1911, the trigger just releases the sear, so it doesn't have to move very far.
In actual operation, the LDA is more like the Glock "safe action" system than a traditional double action only (DAO). In a DAO, whether revolver or pistol, the trigger pull cocks the mainspring AND fires the gun. That's why a DAO trigger pull is so heavy -- it has to overcome the pressure of the mainspring.
In the LDA system, like the Glock system, the cycling of the slide compresses the mainspring. The LDA trigger then just needs to draw the hammer back and release it. Because the mainspring is already compressed, the LDA trigger does not face the resistance of the mainspring. Instead of fighting the pressure of the mainspring, it faces only the resistance of a light hammer spring, and the force needed to release the sear. Hence, it is a "light" double action, or "LDA."
The advantage is that you get hammer down carry with a very light trigger pull. My LDA takes only 1 pound of pressure to move the trigger through the arc and draw the hammer back. It is indeed the smoothest and lightest trigger pull I have ever felt. There is then a clearly defined second stage, however, where the sear releases. Mine breaks at just over 5 pounds, which is about right for a carry gun. If you want, you can easily prestage the trigger at the sear release point. It takes just a little practice to get used to it.
There are several disadvantages to the LDA system. First, you have a much longer trigger stroke than a single action, so a much longer trigger reset is required. If you are used to single actions, as I was, you need to retrain your trigger finger to avoid short-stroking it. You need to fully release the trigger before pulling it for the next shot. In a single action, or a DA/SA, the trigger reset is much shorter.
Second, because the trigger does not compress the mainspring, you MUST cycle the slide to cock the gun. In other words, it does not have "second strike" capability like a true double action. In a true double action, if you have a misfire due to a light primer strike, you can just pull the trigger again. With the LDA, you have to rack the slide. Of course, that's true of single actions and Glocks, also. It's fine with me, as I just practice the standard tap-rack-bang drill with all autopistols, whether LDA or single action.
The bottom line is that the LDA is a sort of compromise between single action and DAO. It has certain advantages and disadvantages of both systems. Whether it's right for you is a matter of personal preference.