Well a lot of the time Trek's attempts at humor are just facepalming to me. TNG(for the most part) tried to stay away from that, while DS9 pretty much just crammed most of their silliness into the Ferengi, which was pretty hit and miss but didn't carry the show. Voyager had a higher frequency of "silly" episodes among the main cast, but yeah... they didn't seem to take themselves seriously teacake. Why should I?
And yes, that's another reason I think Janeway's real bipolar... one week she's cracking witty remarks for humor... the next week she's going bonkers and torturing a member of Starfleet.
My favorite laugh out loud moment in Trek history is Damar's quip to Weyoun's latest clone... "Maybe you should talk to Worf again!"