I haven't loved them on the semi-autos pistols when I tried them, but I have a few on snubnose revolvers.
With my LCR, I was able to shoot tighter groups with the factory front blade/ramp sight, but the dot works better for quick sight acquisition at 10 yards and in. However, that's combining a square gutter sight with a round front sight.
My 442UC/642UC are easier to shoot at more than 10 yards due to having actual rear sights with a U-notch to match the dot. They're also easier to acquire because the green ring is brighter than the white one on the LCR