Laser sights are well worth the money. If nothing else for training, or dryfiring.
When dry firing with a laser sight you can actually see what happens on the target. Really helps in trigger control, which is the most important part of marksmanship fundamentals.
They DO NOT replace the pistol/revolvers sights, they supplement them.
They do work in low light where you can't see your sights.
I'd recommend going to the Crimson Trace Website and download their (free) video and watch it to get some ideal of the value of laser sights.
They are dependant on batteries, but they do last a long time. To be on the safe side, I change my batteries twice a year, when I change my clocks and batteries in my smoke detectors.
I'm against weapon mounted flash lights. Learn to use the light in your other hand. If someone is going to shoot at me, I figure they will be shooting at the light. I want that light extended away from my body, not under my eye which is looing over the sights.
Again, laser sights don't replace the pistol/revolver's sights, they supplement them.
CPT USAR Ret
USAMU Sniper School Oct '78
Distinguished Rifle Badge 1071