I never really liked them and I found them kinda annoying but yeah, they're strong. I had a really easy time with the Elite 4 in Pearl, until Lucian. I had trouble beating him and it was by luck. I mean a Machamp versus a Bronzong using Cross Chop? Yeah, those things are strong, and I find them annoying in pokémon contests.
P.S. in the battle against Lucian it was one on one, Machamp vs. Bronzong, everyone else fainted and Machamp's HP was red