I once had a short conversation with Max Levchin (of PayPal fame) and the one thing he said that stuck in my mind -besides all the drivel about how Slide was going to change the world- was that 10% of a start-up's workforce should be metrics people, obsessed with measuring the company performance i.e. if you have a ten person start-up, at least one should should be an analyst, otherwise he said, the company is essentially flying blind.
From my own experience, if you can not only master the technical side of working with metrics, but be the kind of guy who can actually ask intelligent, relevant questions and structure them in a way that gets meaningful answers from raw data, then you are worth your weight in gold to any start-up.