I kinda had a hard time with Trip at first -- something about that "twangy" accent and his persponality. I flat out disliked T'Pol in season 1. I started to warm to Trip in season 2 with the episode where the crew went a little bonkers, can't think of the name of it right now. I really started liking T'Pol in season 3 when she finally started to come apart at the seams. She was too perfect in season 1 and was obnoxious about it.
Liked all the rest of the ENT characters.
TNG - Wanted to airlock Riker - that never changed.
DS9 - Wanted to airlock Julian
VOY - Wanted Janeway, Chakotee, and Neelix, gone. I'v since warmed to Janeway some.