Changed G19's stock connector to Lone Wolf 3.5# connector. The change made an immediate difference on my 15 to 25 yard targets, but not much discernible difference, if any, on closer ones (7, 5, 3 yards).
Unsupported offhand accuracy at 25 yards went from aggravating ten-inch or twelve-inch groups to slightly improved eight-inch groups (taking my slow time). At 15 yards, it seemed much easier to shoot with a fair amount of speed, putting holes in a 3-inch circle, which surprised the heck out of me since, before, I couldn't reliably achieve that kind of accuracy at that pace as I seemed aggravatingly inclined to drop shots by jerking the stiffer trigger. For closer ranges (seven yards or less), at which I want to blast rounds into an eight-inch circle as fast as I can, I can't tell that it makes any difference.
As far as the before and after trigger pulls compare, the before pull was noticeably harder, but once it broke, it broke. After, the pull clearly feels lighter, but there's maybe ¼ inch of squish before the trigger breaks and the gun fires. Reset appears unchanged.
Swapping out the connector is the only modification I've made. After fourteen years, the sights are still the original plastic ones, but I've replaced the worn out recoil spring, replaced a broken extractor and trigger spring, plus added a few new magazines, though the originals still work just fine.