By uploading those page objects to Amazon's S3, my web server can simply focus on rendering php pages, and not worry about serving images and other static content. I expect the modest expense to pay for itself in the additional capacity that each single server can offer. This will reduce datacenter equipment expenses, and administration time, so I'm all for it.
I like the idea that I can manage an S3 account via a plugin in my browser. I've been using Amazon's Ec2 and I manage it the same way, right from my browser.