I have quite a few guns equipped with Crimson Trace.
I think even in bright daylight they work for my eyes. I find it hard to see the front site and the rear is of course worse. I can see everything well from 15 feet to infinity. When I compete I use glasses that focus right on the front sight but then the target is tough. When I go about daily life I use the variable progressive lenses but when shooting it takes a long time to find the sights.
With the Crimson Trace I can focus on the target look down the barrel, the sights are there but pretty fuzzy but the dot is right where the round is going. I can see the dot on the brightest days to 15 or 20 yards. If I got in trouble beyond that range I guess I have a bit more time to find the sweet spot in my glasses and will use the iron sights.
I recommend them to all my students and friends. My wife and daughter have them on their guns too.
Better to have them and not need them, than to need them and not have them.
I agree with some of the other opinions, about just another tool in the box, don't depend on just them etc… but I also think you should practice with them in daylight doing lots of target transitions and weak hand, strong hand shooting. I like to keep fiber optics on my guns also, if it is to bright out to see the dot, the fibers ought to be jumping right out at ya.
P.S. I wish they made a more compact grip for the N frame, I had to cut down the Hog Hunter on my 629 for carry. I would buy 3 more if they would.