Oh yeah? Like when for example?
Saving Zoro, Nami and Vivi from Mr. 3's wax
Freeing Luffy from Miss Goldenweek's colortrap
Mostly responsible for defeating Miss Merry Christmas/Mr. 4 - Chopper would probably have fallen to them without Usopp
Building Nami's Clima-Tact
Continuing to keep Merry afloat
Saving Nami and Sanji in Skypiea
Getting the giants to turn against the government in Enies Lobby
He's been a big part of the action in the recent story arc as a whole, even if he isn't "kicking ass and taking names" as some seem to want to see. You think these are all menial tasks? They aren't any less important just because they aren't so flashy. The reason why Usopp is my favorite character in the series is because he has so much more variety of plot involvement, and he's not just a fighting machine. If you think about it, Zoro really doesn't do all that much lately. He trains, he sleeps, he fights. I can't relate to him, I don't see any character development happening. Usopp and his haphazard, not-so-glorified adventures are far more intriguing and fun for me.
I've said it before, but Usopp reminds me of the hobbits in Lord of the Rings. They never become kickass warriors like Legolas, Gimli and Aragorn. They're small and weak, albeit have great endurance, they often feel they are inadequeate and "baggage", but their part in the journey is irreplaceable.