The point about finding the gun itself in the dark is a good point. When I look over on my nightstand, the only thing I can see are the nite sights glowing on my Glock.
Three things made me a big believer in nite sights:
If you take a formal training class, they usually have at least one night portion of the class. You will quickly discover that shooting at night is hard enough without also not being able to see your sights. It is possible to use yoru handheld flashlight to see the target and the sights, but this takes more dexterity than I can manage. Nite sights eliminate this problem.
Second: I shot a night IDPA match. This brought out the points above as well as a different twist on the same theme. We had one senario where we were in a shoot house but the targets were outside. The senario is that you hear a noise outside. You open the door to see what is going on and three guys are robbing your shed. When you light them up, they turn and open fire on you. That particular night there was a very bright moon and you could see the targets easily and distinctily. However, since you were inside the building, you couldn't see your sights. Again, you could clearly ID the targets without a flashlight. It was bright enough outside to see the scoring rings on the targets. But, you, being in the buidling couldn't see your sights at all unless you had night sights. This might be the same situation if you were lighting up your target with a flashlight, or if the target was lighting himself up with a flashlight, or the target was clearly illuminated with light coming in the windows BUT, you are standing in the darkness of your bedroom door.
You often read on these boards about never shooting a target you can't identify and if it isn't light enough to identify the target then you shouldn't be shooting: what these people don't realize (because they never tried it) is that it is easily possible to have the target clearly visible while you are standing in the dark.
Lastly, I have done a lot of jack rabbit shooting at night. We light up the rabbit with a spotlight but again, you are not standing in the light of the spot light. You are well off to the side and can't see your sights. This is just a variation of everything said above but further drove the point home to me.
One more thing: if you have nite sights, this gives you just one more option/advantage. If you don't need them, there is nothing negative about them. You just use them like any other factory iron sight. But, if you need them, they are there.