I've tried them and now use them for my glow rounds. They are super bright and the batteries are replaceable. Some people may view them as a little pricey but if you play even a few rounds of glow a year they pay for themselves. I have 2 discs outfitted with them.
The hardest thing to grasp about these is that you are destroying a disc that will no longer be useable for sanctioned PDGA play because you are putting a hole in them. For us junkies with way to much plastic anyway converting 2-3 discs for permanent glow use is not a big deal. I just used some new plastic that I was fine parting with.
Each light comes with a little tool, almost like a leather punch but its a disc punch. You hammer a hole into your frisbee on the underside nub, and then push the nub on the light through. Its not a easy as they lead on in the instructions but thats cool with me because that just means its more secure. Once the light is through all you need to do is depress the switch on the underside of the disc and you're GTG.
They have a solid mode and a strobe mode and are way brighter than anything else on the market. The adds say it does not effect the flight of the disc but I have found that it makes less stable at high speeds. I converted a champ boss and a z buzzz. The boss has maintained most of its stability but the buzzz will flip if you rip it, but at slow to high-mid speeds will maintain its intended flight. The hole in one light also adds about 10 grams for whatever that is worth.
I have one more light that I want to use but I still have not decided on the right disc, I am leaning towards a leopard probably so ive got something in between the boss and buzzz.
Overall I think that its worth it for thoes who play a fair amount of glow.