I've had my new 2009 SM5 for about two weeks now and put about 450 miles on it so far. I'm starting to get the hang of it after being on two wheels for 25years. It's been more of an adjustment than I expected, but I'm liking it more with each ride.
I also noticed this extremely annoying whine or whirring sound since pulling out of the dealership. On mine it seems to happen while coasting at low speed coming to a stop with clutch pulled in or not. It's worst is between 25 mph through to stopping. The brakes have no affect on the sound. I got a shop manual to see how to adjust the belt because it felt too tight to me and hoped that loosening it up a bit might fix the problem. I don't have the specified sonic tensioning tool that's in the book, but I did loosen the belt a few turns and align it properly on the sproket. Mine was against the sproket wall and is supposed to be 1 to 3 mm way from the inner wall. This did seem to lessen the sound some, but it's still there. The belt is still fairly tight so I may loosen it some more to see what happens. I'm just not sure how loose is too loose. I also plan to visit a dealership or two and see if I can take one or two others out for a test ride and to see if it's my bike or just an embarrasing annoyance that goes along with this machine.
I also backed off the parking barke adjustment a bit as well. After these initial adjustments to belt and brake, it also seems to roll more freely over all (less drag in general).
In my case, the brake adjustment had no affect on the whining/whirring sound, only the belt adjustment did. I can only hope that they didn't overtighten my belt from the start and damage a bearing.
I'll know better once I hear a few other Spyders.