My personnel experience for what it's worth. I own two AR15 and have the BAD lever on both of them. Now I've trained with the AR15 for many years before the invention of this device. The stock AR15, although a great rifle, has some draw back on clearing jams and speedy re-loads. The BAD lever really helps speeds the re-loads and makes for one hand bolt back operation, which for me speeds up any FTF or FTE. Now, this means the world in combat and L.E. environment, for the casual plinker shooting paper Zombies, it just looks cool. It requires new training and skills to learn how to use it fast. It's not a bolt on and the unit improves the rifle, you must train and improve your skills to make it function well. It works for me, I now need one for my M&P 15/22 so I can continue that skill.
Many may say to keep the AR15 "KISS", I too agree, but every once and a while a good idea comes along and improves the operational value of a weapon, I'm all for that. Good luck. I'm waiting because I don't want to purchase the BAD and heat it up and bend it to fit the M&P 15/22, I can wait for one made for it, soon, hopefully real soon.. just my .02 cents..