I think out of all the inventions to come along, the wheel still stands at the top of the list.  Boating was great, but it could only get us around on water, and it was pretty slow.  Flying is cool, but it still uses wheels to gain momentum to take off.  Walking is great but it’s pretty darn slow.  Biking is great exercise like walking, goes faster, but also uses the wheel.  The lazier option, cars, are perhaps the greatest mode of transportation ever invented, but once again, they use wheels.  If they didn’t have wheels, even if they hovered, they wouldn’t be nearly as safe as they are.