Our operation has gone from full conventional tillage, to ridge till, to no till and a combination of all of them and now we are back to ridge till for the majority of our acres.  We cultivate an average of 800 acres of corn and 800 acres of soybeans each year and not one time have we said "let's cultivate to increase our yields."  Some times stuff gets one pass with the cultivator and sometimes it gets two.  Weed pressure is the determining factor for extra passes. 

Our cultivating/ridging roots go back to the days of gravity furrow irrigation and we've migrated back to it to give us a consistent seed bed in spring and for weed control later on.  I'd venture to say that my 16R/30 cultivator has paid for itself multiple times when one figures it is hard to spray beans for less than $30/acre and get a decent kill!  I'm fortunate that my father still loves to cultivate and GPS makes it easy.  We have three sets of sweeps ranging from 15" to 19" wide.  If our rows are in the right place 19" does an amazing job of weed control and we can cover two quarters a day relatively easily.  The record is three in tall corn going 9 mph.