I have a CT on my 642. Granted, they arn't that great in bright conditions, but I can see my sights if its that bright. Then again, in low light conditions, the CT works well.
As mentioned, dryfiring with CTs is a great training tool. You see what happens when the hammer falls. (I'm a huge fan of dryfiring).
Check out the CT videos posted on their site (the link is posted above).
Now, my one and only complaint with the CT laser sight is;
WHERE WERE THEY WHEN I WAS IN LE AND NEEDED THEM.
I tried all kinds of night sights, glow in the dark sights, etc, Nothing compairs to the laser sights. Now days you see all kind of gimics, Rails, flashlights, all kinds of crap that goes on revolvers/pistols. They are fine if you are into BuckRogers crap, but totally impractal for a Street cop or even SD. I carry a little 642 in my pocket, yes there are better, heavier guns but I found a small pistol in the pocket beats a heavy gun in the truck. You defeat the purpose with attached flashlights & such. Same with a duty revolver/pistol. Totally impractical carrying that crap on your duty holster.
The CT sights are differant. The grips for my 642 are no more bulkier then the orginal grips. Yet I have the choice of using either the laser or sights.
If you dont want them on a carry piece, fine, but I think they are worth the price if use for nothing more as a training aid. In Dry firing.
Just the night before last, I had my wife dry fire my 642 w/LS. She was all over the place. After seeing what was happening, she concentrated and in less then 20 min she was keeping the red dot inside the X ring of the 50 FT NRA RF target at 20 ft.
A war story. Last fall I went out side, it was dark. I heard a rattling under my steps. Not taking the time to fetch a flashlight I lit up a rattlers head with the CT dot, and shot him. I couldnt see my sights. I have Grandkids running all over the place. Grand kids and rattlers dont go well together. I dont always have a flash light, I always have my 642 w/laser sights.
JMHO