The feature I most want from AWS is a simple way to create credentials that are only allowed to read from or write to a specific S3 bucket.

The way you do this at the moment genuinely involves copying and pasting JSON policy documents around! It's horrific.

I want this for myself, but more importantly I want it for users of software that I write. I would love to be able to build something that stores a user's data in an S3 bucket that they own (and are billed for directly) - but it's currently just too difficult to talk them through setting up the bucket and creating the right credentials for it.