Great post, but I do disagree with this:
but it's a hell of a lot cheaper, faster and easier than running such a cluster
This is at best only true on a small/medium scale, but ultimately it really depends on your use case and how on top of your AWS bill you are. My contention is that once you get to the point that you're running thousands of large EC2 instances, you'd actually find it cheaper to deploy and manage servers in your own DC (or a colo).
I'm sure the folks at Netflix will disagree with me, but considering the hundreds of folks they have dedicated to tooling and optimizing their AWS deployment, I'd say they're a special case (plus they likely get big discounts given the amount of cheerleading they do for AWS).