For me a few things,1. bikes my parents wouldn't buy me as a kid,2. I love jumping on one of my fully rigid retro bikes after being on my downhill bike all day and going for a blast along the local trails at the night time. You can obviously feel the difference between them and then you have to adjust your riding style to suit with the brakes,gears and no suspension and you still get a buzz from doing it,i'll never get tired of that