Let me first say that I am NOT a brony (not a hardcore, fanatical brony, at least). I only started watching the show to see what all the fuss was about, and I don't intend to let the show or fanbase rule my life or govern my interests. Nor will I mindlessly defend either of them.
That said, I enjoy the show strictly for what it is; a children's show, albeit a surprisingly well-executed children's show. The characters are well-written and interesting, the animation is solid (occasional errors notwithstanding), and each episode's plot flows nicely. But really, let's be honest. It's still a children's show, and it was obviously made for pre-teen girls. We can't pretend that it's the greatest form of adult entertainment on the face of the earth.
Personally, I can only take something seriously if it's dark, realistic, or sends an accurate message about the human condition. My Little Pony doesn't really do any of that for me (maybe I'm just too cynical, but some of the "darker" or "more mature" elements of the show just seem cute to me at this point), but does that prevent me from enjoying it? Not at all. Sure, it's far from being as dark or sophisticated as I would prefer, and I don't really find the show's humor all that funny (it's still way funnier than Family Guy, though), but it doesn't have to be. It's a nice little show that provides escapism from the hardships of reality without insulting my intelligence or being nauseatingly girly (I'm looking at YOU, G3). And I respect that. It doesn't necessarily sell itself to adults, but it doesn't alienate them, either. The show works the way it is, and don't let it's cute, feminine image put you off. I accept the fact that, at it's core, it's a show meant for pre-teen girls, and I don't have to take it seriously to like it.