Ask HN: What is the battery life really like on i7 laptops?

I'm trying to decide between a high-end Core 2 Duo and an i7 for my new laptop. On the one hand, I keep hearing that the i7 regulates its power output very well depending on demand. On the other, the reviews I've read gave wildly varying battery life stats for the i7. Can any of you share your experience with an i7 or a high-powered Core 2 Duo? If not, can you at least speculate with me? Thanks.