I debated what optic to get, for my shield plus, and settled on the always on Swampfox Sentinel. The shield isn't cut yet, so I can't give you a firsthand account, but I wanted the auto brightness feature of the non shake awake one. I didn't want to have remember to adjust brightness every time I went from indoor to outdoor and they estimate two years of battery life, for the always on model. That being said I have shake awake on my long gun sights and they work fine.Just got my 507K a few days ago. It's already on the way back to Holosun. The "shake-awake" never worked. I tried all the recommendations and troubleshooting, reading the manual, etc. It only worked if I gave the side of the gun a good whack. Even racking the slide wouldn't "wake" it up. That thing was harder to wake up than a teenager. I think they've already shipped a replacement, though. If that's the case, good for them and I'll be happy if it works as advertised. It seemed like a pretty useful piece of gear and worked well otherwise.