My night sights have become very dim over the last 13 years. I replaced them with heine sights (regular). With my LE job, I've found when I do unholster at night, I have a flashlight with me. As long as the target is illuminated, you can find the front sight. If the target is not illuminated and cannot be identified, you should more than likely not be shooting. In that instance, firing would only be for cover fire, which would not be advisable due to not knowing where your rounds are going.
On the other hand, my father likes the night sights due to his eyesite diminishing with age, a lot easier to find that front sight in low light.
To sum up... personal preference. I really don't have a use for them. My co-workers could find me very easily when sitting on perimeter because of the glowing sights (at least the ones at the right angle, so could bad guys). If you want to spend the extra, and it makes you more comfortable, by all means get a set. We have many at our dept. that have the sights and would not have anything else.