I don't understand the weight issue. Theoretically, a couple of pounds on a bike should make no more difference than a couple of pounds on a rider. I have a good cyclocross bike (Specialized Tricross Comp - aluminum, carbon forks) and like how it rides. But I have rented light weight CF road bikes on trips and was surprised at how quick and responsive some of them felt, particularly on hills. Does the reduction in weight on the bike itself somehow count more than the overall weight of rider and bike?