I have been using nocturnal for a couple years. My problem with them is the small hole on the side of the nock that you need to put something into to turn the light off. its basically like a switch inside that you need something small to put in and flip the switch off. Should you get a pass through on a deer, the hole gets blood in it and makes the light hard to see. it isn't very bright to begin with, but this doesn't help.
I just read a good review about the new carbon express launch pads. They are universal to fit any arrow. You insert them, give a quarter turn and the base expands inside the arrow to give them a snug fit to any diameter shaft. they turn on when the string is released and puts pressure on the back of the nock, and to turn them off, all you need to do is gently pull on them. They only weigh 18 grams, and battery life is supposed to be from 30 to 70 hours depending on what color they are. Carbon express is also pointing out the design of the nock itself and how it makes contact with the string at the same 5 points consistently with all the nocks. This should lend to better accuracy because you wont have that one nock in your quiver that has a little piece of plastic from the mold that grabs the string differently than the next one.
i just so happened to be in my local bow shop today and they just so happened to have them. I bought a three pack for around $25. haven't tried them yet, but from playing around with them at the store I can say that they are easy to turn on and off, they are bright and they seem to be well designed. i do like the universal fit, i could take the nocks out of my easton arrows, and put them in my daughters gold tips.
I'll let ya know what i think of them after I get a chance to actually shoot them.