Linz, I've had a 17T c/s sprocket for about a year now. 60 MPH (96 KMH) is now 4K RPM...I forget what it was before. :hammer:
Fuel mileage, overall, hasn't changed. Easier to start off from a stand-still, stronger acceleration, not too short for highway riding.
While I'm not showing any wear problem, I think when it's time to replace chain and sprockets, I'll go 18T/44T, which is almost the same ratio as the present 17T/42T. (The '02 DSSA D955i here did wear through the rubbing block w/the '04's old 18T, but is now a 18T/46T and very responsive. :-D )
Brad