I've used Luminocks and Tracers and I don't care for either. The luminocks add too much weight to the rear of the arrow and actually cause your arrow to hit high. as much as 7"at 30 yds for my set up. The tracers were a pain as they needed a magnet to turn on and off and were also heavy.
My solution came about this year with the Nocturnal. This nock only weighs 20 grs (that's only 7 gr over a std nock). I shot them on a 3d course last weekend side by side with my regular nocked arrows and could find no difference out to 40 yds. There were no failures to light and were highly visible (green).
All this being said, the nock will help you see your arrow hit but it will not help you kill the animal. There is nothing that will replace a well placed broadhead in the vitals for a quick humane kill.