I've always sort of liked the cheeky response, inspired by Russell, to the fine-tuning argument: there's not a chance in hell that God would have designed a world like this, so I'd say the probability that God exists given the appearance of fine-tuning is nil. Not everyone finds this response convincing. ([tic]Maybe they like fascists and Klansmen?[/tic]) Robert Howell linked to an interesting discussion of fine-tuning here. Take a look.