I have a laser on my 642 and I like it. It doesn't replace my sights, it supplements them. So what if the battery goes dead, that doesn't mean you can't use your sights. But I've never had a problem with batteries. I change them (though they never needed changed) when I change my clocks twice a year and at the same time I change the batteries in my smoke detector.
As for giving away your position, DON'T ACTIVATE THEM UNTIL YOU ARE READY TO SHOOT.
On my 642 I can't really tell the difference on the grips between the orginal grips and the CT laser grips.
Now for the biggest advantage of the laser: Dry firing, you can really see whats happening when you dry fire. The dot don't lie, if it jumps off the target when you drop the hammer, it means your shot will jump off the target. Great tool for teaching trigger control.
Another advantage, (dry firing related), and you can try this at home or range. When my shooting starts to go south and it will with these little snubbies, I stop shooting, dry fire for 15 min or so and then back to the targets using iron sights, and my groups get tighter.
I shoot 98% of my practice using iron sights, even pay to shoot a second gun so I can shoot my 642 in ICORE matches. Dry firing with the laser helps a lot.
Another trick, or should I say shooting game, when I was in LE I carried a little mechanic's inspection miror for building searches without exposing my self while peeking around corners. Now I found a new game. Using that same inspection mirror, I can peek around a cornor, see the target, put the red dot on the target and shoot, exposing only the gun and mirror. Now I'm retired and doubt I do any building searches but its still a fun game and in all honesty, thats what most of us do, shooting games, matches, practice, plinking, .........just having fun.
Many who condem Lasers seem to think that once you put a laser on a pistol/revolver, its all you have, with the laser you can't use your sights, you can't point shoot........all you have is the laser.
That's a long way from the truth. Its a tool, just like point shooting, using sights, what ever, another tool. To me the greatest benifit of this tool is in dry firing.
The CT Laser grips does not add bulk to my 642 witch I carry in my pocket. The lasers for some pistols/revolvers do, I don't thing I would like those, but on my snubby its great.