Gave MLP:FiM a real test: my brother. I was rather certain he would dismiss it before giving it a real chance (though he was certainly willing to give it a cursory chance) but I can tell he enjoyed it. I'd describe him as a "closet brony" at best though. I can't imagine he'd be downloading and watching all of season 1 any time soon.
My parents, on the other hand, thought I was just fucking around with them when I told them I watched My Little Pony, but I told them it was awesome. Then, while watching it, awpmom swings by and says "Wow, you really ARE watching My Little Pony". About 20 minutes later, my old man comes by and says "Holy shit, she was right - you ARE watching My Little Pony. Why are you watching My Little Pony?" Good times. And now I can probably expect some kind of MLP paraphernalia for Christmas. Just please, nothing related to Rarity.