I love the smaller motorcycles for putts'n around -- and that's what commuting is to me -- at least when I drive. I've had a motorcycle all my adult life (30+ years), until about 2 years ago when I sold my last one because I felt bad that I hadn't ridden it in more than a year. I've found the twin cylinders I call thighs get me around traffic fast enough with a heck of a lot more fun taking the MTB trails along the way. It's still 2 wheels, and really good gas mileage!
Yeah, I'd go for a small displacement motorbike again, but probably not till I get a lot more more grey hair and wrinkles.