I'm using it. (pics in the painted glock thread). When its "Charged" its super bright. The intensity dies down after a bit. Within 4-5 hours, you can hardly see it.
It is not easy to spread. From what I understand, brightness is related to the size of the glow pigment and the V10 (brightest) stuff they have, has some pretty large chunks of pigment.
I did the front and the rear. This glow is after about 10 seconds worth of "Charge" from a TLR-1 tact light.
It would be good for "open" rifle sight as their exposed to sunlight/light most of the day (as opposed to in a holster) and in twilight, the sights would glow enough for you to see sights.
HTH
D