In both my old stock tires, and especially in my newer lower-profile tires I saw a dramatic difference in coast-down speeds on certain long, sustained downgrades. This was most dramatic when I last went in for maintenance and my pressure was lowered, coastdown speeds dropped, then later that afternoon, the coastdown speeds returned to normal when I refilled them. MPG difference is small but definitely observable. The handling/steering feel difference is much more prominent, and the main reason I prefer high pressure.