They're a little buggy, they use some slightly new mechanics. They're about halfway between a mount and a siege vehicle. Your action bars don't change or anything like that, but it is definitely considered a vehicle since a passenger can hop into your sidecar. It's also not Engineering only, but I think that is so they can get extra testing done on it. It's a seriously cool mount, and one I'm pretty okay with. If Azeroth can develop helicopters, airplanes and submarines, they can build motorcycles, too.