I'm not sure if it's my imagination, but sometimes I feel like I'm at a disadvantage on a carbon bike in the wind. My Aluminum framed bike gets blown a bit in a strong crosswind, but sometimes my carbon bike feels like it will fly off the road from under me. The light bikes affect acceleration and climbing mostly...overall calorie burn or work load is probably down too for a longer ride, but not by too much. Wind resistance is the enemy, not so much gravity.