I never had one until the A1 either, although I'd heard about it for years. It's fairly common knowledge. It says that if you continue and something goes wrong it could void your warranty. And they will know, the camera records it whenever one is used. I use PowrExtra, Wasabi, and a few others. Nothing wrong with them, accurate and they last about as long as a factory battery. I don't really worry about it to be honest, it's more of a pain in the ass than anything. You have to accept the message, which then makes the message go away until the next time an aftermarket battery is installed. The problem is it doesn't show up right away, it seems to pop up a couple minutes into shooting. I do a lot of fast shooting where the camera comes up to my eye quick and I'm already hitting half-press. I see the message for a flash, but it disappears when I shoot. Then it keeps popping back up until I acknowledge it, but it just feels random.