I got very excited with S3 first came out, but I found when designing several schemes to make some profitable use of it, I'd find prohibitive limitations in its functionality. Is it just a fancy cache, or could it/should it be something more? What would you add to it, if you could?

I'm interested to see what people say here.

I've been using S3 for some time; my primary complaint is the lackluster performance. So my request would be additional caching to accelerate things far away from wherever the S3 data center is.