I thought Pertwee was fine: good actor, made a good impression in the role. His first season was excellent - more adult like in its approach than Jon's subsequent seasons.
Slightly let down by his main assistant - Jo Grant . Katy Manning often seemed to play her role as an awestruck fan girl which was sometimes embarrassing to watch. She wasn't all bad - she played her part beautifully in Green Death - gradually growing apart from the Doctor and falling in love with that welsh chap.
I have read that the series was on its last legs when Pertwee took over, with falling viewing figures and the BBC seriously considering cancellation. In my opinion Pertwee was instrumental to the success of the post Troughton reboot. Without him we might not have subsequently seen Tom, Peter or Colin in the role. I think that is a very good reason for liking him.
Finally he played Chief Petty Officer Pertwee in the Navy Lark. Magic.