They don't help you aim more accurately. All they do is glow in the dark so that you can actually see the sights in the dark as opposed to trying to line upo something you can't see. So, I guess in that regard they help. They are generally pretty crude, but again in the pitch black they are better than nothing. Most require a hit with a flash light to get them to glow, since they are not tritium filled.
I have some East German ones that just clip on the existing sights.