It's a word filled to the brim with irony, for in a way it describes itself. Pedantic means in most contexts: ostentatiously learned, unimaginative; pedestrian. The word itself is longwinded, and unnecessary. Today it exists only to show the speaker's prowess in vocabulary.
It's a poor, redundant, and abused word. Sure people exaggerate, and sometimes they want others to understand they are no longer doing so, but most people using it in speech just use it to amplify their exaggeration. My point is, use it right or don't use it.