In this article, the NYT assesses the life cycle of steel. As you'll read, it's not such an earth- (or human-) conscious mining and manufacturing process...
But ultimately, the writers say that if you plan to have more than one drink of water in your life, stainless steel is still a better choice than plastic bottles.
I think maybe we should go back to the writers' other suggestion: drinking fountains.

Adam W. says:
Like you said, it is all about the lifetime footprint. Stainless steel has a big initial footprint, but it should last you years, if not an entire lifetime afterwards! They are durable beyond belief. I actually tested one of mine by dropping it out of the 10th story of my office building - a little scuffed up to be sure, but it still works great!
Jay G. says:
Maybe it's more green to steal your friend's steel water bottle.
Adam W. says:
Hey buddy - give that back!
Bill S. says:
The scary stories about plastic drinking bottles just keep on coming. Stainless steel bottles answer the main eco question -- they're reusable and anything that can be used over and over again automatically lowers its carbon footprint.