There's a thread on m4carbine.net called "Looking for a flat, straight Glock trigger? Pull up a chair and come inside", where the poster reviewed a bunch of these triggers. I'd post a link, but for some reason I can't find it - not sure how I found it before.
Anyway, based largely on that thread I bought an Overwatch Precision trigger for my Glock 19 range gun, and soon after trying it, I installed the same trigger on my carry G42 and G26. Yes, it reduced the trigger pull length by eliminating a lot of the pre-travel, but it did not lighten the pull weight (you need to install a minus connector for that) and the reset is the same (which is good). I think the most important thing about this trigger is the flat face and the fact that the trigger safety depresses completely flush with the trigger face. Just because of the trigger shape, I can use the pad of my trigger finger instead of the 1st joint, and you basically can't push or pull the gun off-target because the trigger doesn't give you anything to push or pull sideways against - you almost have to pull the trigger straight back. All by itself, this trigger eliminated my tendency to shoot low/left on all 3 guns.
Overwatch Precision goes to pains to explain why all of the safeties continue to work, and I have had no issues on any of the guns.
These triggers are $130 or so, which seems like a lot since I think that the most important benefit is the trigger shape. If Glock just provided a cheap plastic straight/flat trigger on their guns, most of the advantage of these aftermarket trigger would disappear. However, for $130, Overwatch Precision does give you a beautiful, machined and anodized trigger, plus an NP3-coated trigger bar, all of which seems to have been carefully engineered to maintain reliability.
I used to be one of the "stock parts only on carry guns" people, but now I realize how many corners get cut & compromises made on stock guns (rough trigger group surfaces, weird trigger shapes, heavy triggers for liability reasons). If I can clearly improve my ability to put shots where I want, and I can verify that the gun remains reliable, then I'll modify the gun.