I tried one about a year ago. I must have misread it because I thought it had tritium and it doesn't. The dot is rather small and didn't collect enough light for my tastes. The concept is different and kinda cool. I ended up sending it back for a refund and getting the Ameriglow Hackathorne setup for both my G21 and G30.
Certified Glock Armorer
"The 21 Club" member #3263827