MeanJoePhaser
Admiral
My Worst Thing in Trek (meaning something pervasive, not individual characters or episodes) is the tendency towards episodes where the characters fly in, solve the wrongheaded aliens' problems, give them a lecture about the superiority of the Federation, and fly away.
Either that or technobabble. Or the abuse of time travel.
Isn't all that Star Trek in a nutshell? Try hard to think of an episode that's free of any of those three things...er...
I dunno...in a similar vein, I personally lost interest in the new Dr. Who because he's such a morally superiour twit so much. Yeah, guns are bad. Humans are screw ups. Whatever.