VNAV works great in climb on a 757. Descending VNAV brought up the power a lot so I didn't use it much. Found FL change more efficient with an idle descent all the way down. I usually flew over the VNAV descent point a few miles to not have to add power. I always considered the lower winds in the adjustments but rarely needed speed brakes because I didn't follow the VNAV path. I made a game of idle power from top of descent to spooling up at 1000 ft per opspecs and not needing spoilers or power. I didn't care what the FO did on his leg but it made my leg more challenging.