TVTropes explains one of the reasons the show is so great:

Rounded Character: A large part of the reason for the huge Periphery Demographic. Characters have multiple conflicting motivations (for example, Rainbow Dash's desire for recognition vs. her sense of loyalty), and often bounce off of one another in different ways from episode to episode (e.g., Applejack acts as a restraining force against Rainbow Dash's hotheadedness, but comes off as the Action Girl when Rarity hesitates to get her hooves dirty.)
Also: I get so amused when people get buttmad about pony images on 4chan and I go out of my way to use pony reactions even when another might work better.