Q is my favorite re-occurring character of TNG and VOY. he was the one saving grace of Encounter at Farpoint, quite frankly. But not all Q episodes are good. I didn't like Qpid or Q and the Gray. I like the idea that he is introduced as a villain sent by the Q continuum, and by All good things, it is clear he really is trying to help humanity all along...sort of giving hints to Picard, without giving him the answer, in order to save humanity from the rest of the Q continuum.