Power button changes the shift points slightly to give you better acceleration. Keep the button down however long you like. Some people claim they get better gas mileage driving with power mode turned on all the time. It does drive better, but I doubt higher RPM will help you save gas (quite the opposite). The 4,000 lb funky slug does feel peppier with power mode on and it doesn't do the slug crawl on hills with power mode on either. Try it next time. While going up a steep hill, switch from power mode to normal... instant slug!
Winter button starts the VX off in third gear so you don't sit there and spin tires in first gear on snow or ice.