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

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?