Originally Posted by
f4rrest
The modeling here demonstrates that aero is much more important than wheel weight, even climing at less than 20mph.
http://www.biketechreview.com/archive/wheel_theory.htm
There are some other articles on that site that show lightweight wheels start to make sense when the hill is really steep (around 15% gradient), but it depends somewhat on how fast you can travel uphill as well.
And, most everywhere there is climbing, there is an equal amount of descending. On this planet at least.
The aero advantage is greatest at descending speeds, and certainly mitigates at least some of the weight penalty, IMO.