God, there is so much crap willy waving on here.
53/39 and 12/21 is what Fabien Cancellara uses. If you are not him then don't expect to use the same gears as him.
For the record I use a triple with a 12/27. I very rarely use the low gears, but like having them. I also love spinning past "hard" men on their silly high gears on long hills when they are grinding their way up at about 30rpm, when I am happy at my normal 100ish rpm.
Basically choose what you like but don't let silly people pressure you in to running silly high gears.
Oh, and MisterT, I live in the "flatlands of the SE" and my daily commute includes a 22% climb. Even Pro-teams change their gearing above about 15%