IIRC in one of his books Phil Gaimon was asked about what the toughest climbs were. He said that, for pros (as opposed to us mortals), the climb didn't matter. Any pro could ride up pretty much any climb without too much difficulty*. What made it tough or not was the competition you were racing against and how fast you had to go in order to keep up.

*I think this might have been written before the stage on the Angrilu that [MENTION=186391]indyfabz[/MENTION] lists above.