When you decide, give an update on time saving. Mostly Im curious. Five pounds of of static weight, considering a very fit 160lb rider, plus 20 pound bike, 180lbs. 3% weight differance. Increased rotating mass of 28 or 32's probably makes much more differance.
Personnely, I think you should go for it, I just bought new golf clubs that at best will marginally improve my scoring, but its fun.
I agree, its more likely that the shifters will make more difference, in that you will tend to ride more efficiently. It would just suck if you spend $3500, outit it for commuting and find out it is still ten minutes slower than your Davidson.
Think of me as taking your wifes side of the argument, so you can be prepared to justify your purchase. hehe