I was a little mean earlier and dropped a teaser for the new motorcycle mounts from the Wrath of the Lich King beta on Ask a Beta Tester earlier, so let me make it up to you all. We've put together a little gallery of the highly anticipated (by some) motorbike mounts that were officially implemented just last night, so if you're interested, go on and take a look.
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.
Gallery: Wrath of the Lich King: Motorbikes