Yup, Oak had it. Commit, and get up, all the way. Once you're up, straighten your knees and stand. Well, don't straighten them all the time :-), but do aim for straightening your knee completely from time to time, if not on every pedal stroke.
I stand a lot, sometimes because my legs start screaming on a hill if I don't, sometimes just to catch a better glimpse of the next intersection, sometimes to get a bit of extra oomph to get out of an intersection fast and not have to discuss right-of-way with a driver who looks clueless. It doesn't have anything to do with racing or better or worse, it's just a handy but not absolutely necessary skill which some people like to use more than others.
Winter riding is much less about badassery and much more about bundle-uppery. - malkin
1995 Kona Cinder Cone commuterFrankenbike/Selle Italia SLR Lady Gel Flow
2008 white Nakamura Summit Custom mtb/Terry Falcon X
2000 Schwinn Fastback Comp road bike/Specialized Jett