I bought some yesterday and it is really exciting watching them fly to the target.I imagine during a hunt they would aid tracking the animal after the shot

They certainly look like a asset when shooting at game.
As a member of several organizations that have drawn a line with electronics on bow or arrows I don't use them.

They are not legal everywhere, make sure you check first.  I know they are not legal in Colorado.

I love them from ground    blinds(easy to find after     misses)

Speaking of legality,I tried to find something for Alabama online but couldn't..

And why they look like an asset?could you elaborate?

Chris,
 I've used them (and not) off and on. In low light, they can be an asset to see where the hit was IF there is pass thru or deep enough penetration to put the nock near the hide. If there is poor/little penetration the lit nock away from the animal doesn't help me see the entry point. They help in recovery IF they stay lit, and some don't. I believe that their use would prohibit Pope & Young entry of an animal if you're lucky/inclined to kill a P&Y critter.
Overall, I rarely use them but if you're after those South Alabama hogs.......
                      Good hunting,
                         Todd

but they do add weight to the back end of the arrow

El Greco, Paraphrasing the Colorado regs. they are an electronic aid attached to the arrow and therefore not legal.  I don't use them for a variety of reasons but not being legal is one.

Legal in Texas, and I've used them plenty. Work great in low light. In the middle of the day, you can't tell a difference.

I don't use them anymore, but if I had them and they were free...i wouldn't hesitate to use them.

I use the nocturnals and love them. Never had one not work. Helps on hits, sure helps find an arrow wether a pss thru or miss. Two deer have still had the arrow and lit nock in them allowing me to find them faster. In our early season I will do everything ( lighted nocks and string tracker )I can to find downed deer quicker. In 80 degree heat an hour or two can make the difference in meat or waste.

Not me..not yet anyway..may some day.

I've used them, really liked them too when they worked.  Seems like they would only last about a week until they went dead.  This was about 5-6 years ago so maybe I'll try the newer ones and see if they work better.

The Nockturnals are the best I have used so far. I hunt with orange feathers because I love to ground hunt and I always have one arrow with a lighted nock where legal for late or early because my feathers are hard to see in low light. I think they would be a good deal in turkey season if you just hunt natural cover cause you could fletch with natural color fletching and still see your arrow in flight.

They work well where legal. If pass thru helps with impact point(seeing it disappear), if incomplete penetration may aid in location of quarry.

Shooting target arrows near dusk at a distance is cool if you like the arch in archery, and helps your brain understand trajectory.

Back in my wheelie days my son talked me into them. At that time they were all very unreliable and we tried lots of them.  But in reality bright fletches always worked better for me except in extreme low light conditions when looking for a lost arrow.  If they work, they work great for finding lost arrows in the dark.  I don't use them anymore.  I also don't shoot when it's too dark to see good enough to follow the fletch.  There have been several missed / passed opportunities accordingly but I am ok with that.

I think Eflanders says it for me; if you're shooting when it's too dark to follow the fletch, is it too dark to ethically take that shot?  I'll pass on that situation, so obviously I don't use them.

They won't fit on the back of a douglas fir shaft, so they're not something I'll mess with.

White cap dip and three white fletchings are good enough for me.

Tried them once ,shot and the other 5 arrows in my quiver lit up!!! Gave them to a friend..

Went to a shoot in Topeka. They had a night shoot with glow in the dark targets under 10 yards. Used some and got a good laugh. Kinda fun.