Excuse me guys, but unless you hang around places where folks lay on the ground looking under bikes a lot, I seriously doubt it will be obvious to anyone. However, I think Twolane is correct, it probably won't fit into the available area on a Harley without modification.
The advantage to these valves on cars is at least three-fold. First, there is no chance of stripping out the oil pan from repeated removal and installation of a drain plug. This can be very important if you let the kiddies at Jiffy Lube change your oil, or you're the type who often strips stuff. Second, it is nice and clean when you use the nipple version and a vinyl or rubber hose to drain the oil. No splashing, no dropping the damned plug in the hot oil (butter fingers), etc. Third, if you don't have a lift it's much easier to just reach or slide under the car far enough to stick the hose on the nipple and flip the lever, versus getting under there with a wrench. I've been using them for at least 15 years or more on cars and SUV's, and it's one of the first things I buy when I get a new vehicle. One of these times I'll actually be smart enough to remember to remove it from the old vehicle before I sell it so I don't have to keep buying new ones. Duh!
Jerry