One of the 1st things I did was put on a 16 toother (so easy to do, how could I not). I didn't get out much before the switch so I can't really comment on speeds before hand, but with the 16, I get around 65-70 mpg and comfortably hit 60. Over that it starts to get really buzzy and high revved.
Wondering about getting a 1 tooth smaller rear sprocket to take down the revs a bit more at the top end. From what I can tell, there still seems to be enough of power left, I'm just starting to run out of revs. over 65ish.