Very important to some, not to others. I find them best for low light practice situations as opposed to total darkness. In total darkness one should be using a tactical flashlight to identify the target. Of course whereas most combat situations where a CCW would be used take place at under 7 feet and involve point shooting anyway some say no.
Do a search. This topic has been discovered at length.
Whichever way you go this, keep in mind that while night sights allow you to better see your sights, they don't help you see the target. I would strongly encourage you to purchase a tactical flashlight, such as Surefire, Scorpion, or equivalent. The Surefire G2 is about $35. These small lights are not only usefull for "night-fire" scenarios, but for all sorts of situations where you need to see better.
Do a search and you will get a number of threads. This thread is a bit contrary to the general take that they are a good thing. I have spent a lot of money on night sight upgrades and have personally concluded that for the most part they are useless - although harmless.
I have researched it by firing my gun during twilight and low light conditions and have concluded that
1) In general, they aren't any help in low light (twilight conditions). This would be the low light that would allow you to ID the target as hostile but not enough to see your sights well (especially if the target is clad in dark colors)
2) If it is dark enough to see the night sights, it is too dark to ID the target (at least for my eyes). Now maybe that would be useful if I got attacked in the dark, but at grappling distances I'm not sure the gun will get to sight level anyway.
3) I find the 3-dot configuration on my sights distracting in regular daylight shooting. I find the straight-8 configuration and the Novak bar-dot more usable than the standard 3-dot configuration. With the 3-dot, my mind doesn't know whether to work on the problem of aligning the dots or the sights. This is a matter of personal preference, of course.
For me, the ones that Wilson makes (IIRC they're called the combat pyramid sights) are pretty good because they don't have a white outline on the inserts and in most daylight conditions they aren't very noticeable, but are plenty visible at night.
Your call. I don't see them hurting you unless you plan to get shot at by people with night vision equipment where your own sights would light you up.
See if you can try some on someone else's gun before you make your decision.
Since your question is for CCW purposes only, my line of thinking, for what it's worth, is that if it is dark enough for your nitesites to kick in, it's probably to dark to properly ID not only your target, but whether or not it's a threat or not.
You will have to evaluate your own circumstance and make your decision based on your need.
For my circumstances I would never own a serious use weapon with out night sights. I have only had to use them a few times but they were critical in those instances.
They are CHEAP! They only cost about $50-$75 more than the same sights with out the night inserts. They last 10-12 years. If you replace them after 5-7 years to maintain maximum brightness you are still only paying about $10 per year of use.
When I talk with people who had to make shots with out them they really wish that they had had them.
I do not fully understand the arguments against them because they run counter to my personal experience. When bullets are zipping past you should be moving to cover and that will often put you in an area of shadow (deep shadow may be the only "cover" available). At that point you may find that you can make out your threat but not your sights.
If the extra money is the issue I recommend saving up for and extra week or month and get them.
All my carry guns have them too. I like a good flashlite but who's to say that it won't fail you when you need it the most. Night sights are a great backup, and I can see a glow off mine in enough light to still see the target. Another situation they are useful in is when you are in a heavily shaded area shooting into a lighted area. The local range has a steep pitched, covered firing area that blocks alot of light on overcast days and the sights glow readily.
My ideal setup is white dots at the rear, with tritium up front. I have to admit that my middle-aged eyes find those white dots much easier to acquir. Sometimes I wonder if I wouldn't be better off just getting all white dots.
I much prefer to see my target, rather than my pistol. I prefer to use a flashlight.
" I have to admit that my middle-aged eyes find those white dots much easier to acquir."
Interesting comment. I find almost exactly the opposite. Since passing about 45 or 50 I can't stand white dots, particularly the 3-dot configuration with the two on the rear sight. Doesn't make you wrong or me right, just different.
As to the original topic, I find the XS Sight Systems version of dotting the "i" works best for me. From the above it is obvious we all are different.
I find the night sights on my issue Glock to be very handy when serching for it in the dark. When it comes to actual performance, I outshot some of my classmates at my academy at night firing when I was still issued a front blade/ rear topstrap notch sighted Smith model 64. The flashlight is the better means of target aquisition, on paper and in real life. That said, night sight can't hurt.