I apologize if these points have already been brought up.
I was really unsatisfied with King Sombra in the season opener. For starters, we barely learned anything about him. Secondly, he was a "Mwahahahaha" I'm evil villain, which isn't even interesting or cool, unlike the other main villains. I think part of my dissatisfaction with King Sombra in general is that it is phrased as a "test" to save the Crystal Ponies. I also don't have nearly as huge an attachment to the Crystal Ponies as I did to other characters such as Shining Armor and Princess Cadence who were developed. I'm not saying that I didn't like the episode at all or that I won't be hanging off the edge of my seat for each next episode. However, I am really not attached to this episode in any significant way, nor do I think it is a particularly good episode, by MLP standards. Just my two cents.