What Windexed isreferring to is commonly called "Z-Targetting". It was innovated by Nintendo in Zelda: OoT. The name comes from the fact that the 'Z' button was used to target and lock on to an enemy. With the changeover to Gamecube, the term stuck.
I imagine that on a FPS, it could be a little disorienting, but it keeps your gun trained on an enemy, so its a good thing.