There is a perceived buzz at somewhere around 3200 - 3800. I say that because though I note it I can't actually find anything that I touch actually buzzes.
This bike is of at least two natures. Low below 3200 is a thumper and at 4000 above is is a glass smooth screamer. It all depends on what you want to do that day. Keep it above 4000 and find some paved twisties and watch your Yamaha dissappear in the mirror. You see the stats don't reflect this as it just isn't something the average article notes. But you will.
I appreciate what has been said above. After getting this bike and riding it I keep having this blond, 5' 2", 105 lb babe come on to me in the most obvious way. This of course would be my wife...she loves this ride:)