I like them a lot, especially since I do much of my practice shooting in the back yard at night, work and family takes a lot of time up. With the flood light on I can see well enough to shoot and the lighted nock lets my mind ingrain the trajectory and point of impact. My young son also likes the cool factor of the glowing nock racing to the target, anything to get the kids hooked. Also as mentioned a very nice tuning aid when shooting at dusk. Don't plan to enter the P&Y deer I have been fortunate enough to harvest so no worries here about that.
There have been a couple occasions when the lighted nock made tracking the animal a little simpler, like following the exit path of the animal if a pass thru was not obtained. Or finding the glowing nock with arrow in the animal from a distance while trailing. In the thick stuff we hunt is had been helpful.