I have a 46 rear on my 08 and I really like it. Stock is 18/43, I've tried 18/46, 17/43, 17/46, and I prefer 18/46 out of them all. It fits fine with the stock chain with plenty of slack for adjustment too.
The bike "feels" as if it has alot more torque. The gas mileage is almost the same cruising on the highway, and didn't drop much riding aggressively...which is most of the time
I don't know of anyone else on the site running 18/46, but there's a lot running 18/45 and they all say that they really like it too. One tooth difference really wouldn't be noticeable.
I love to ride wheelies and the Busa did them easy stock, now they're effortless.