I third the comments. Just got back from a ride -- just for grins I slowly took it from 3000 to 8000 RPM in second. as others have noted, 4500-5500 is like riding a demented cement mixer with an off-center load.
It was kinda cool just putting along at 7500 RPM in second -- the bike is reasonably smooth there, and it makes a scream like you're really doing something (even if you're not).
I could tell I was intimidating the hell out of the person driving the crate I was following, even though I was hanging back minding my own business.
Of course, once there was a break in the traffic coming the other way . . . .