The way I look at it.. we all have some kind of belief system and we're all irrational to some extent.. Its not like we wake up and think, I'm ONLY going to believe whats been proven and/or do whats rational today and ignore everything else.
Religion is only one type of belief system. I'm a socialist. Can I PROVE that socialism is better than the alternative? No one can! But I still believe in socialism because I have faith that my reasons are right... There are millions of examples in our lives like that. Tastes, politics, etc.
Science is limited by the problems it proposes.. so to me its valuable but I can't rely on it for everything.. Plus, we have to have faith that those people who r doing the science r doing it right and ethically. For example, at one time we believed vioxx to be a safe medicine because science told us so. When science told us it was dangerous it got off the market. lol