Sometimes umpires leave us all speechless. However, at the end of the day, the majority of them put in a hard worked game. Instant replay is going to eliminate some of them. Also, with then new "on screen" strike zones that can tell the viewer where a pitch was, some of them will have to do a better job at balls and strikes.
I think the all time moment for umpire incompetence was last year when Armando Galarraga lost his perfect game on call by Jim Joyce.