My Amazon AWS account has been quietly dust for over year, though a number of recent and current projects are a good fit for the PaaS paradigm especially with Amazon's Virtual Private Cloud and the recent news of their ISO 27001 certification.
This makes it an interesting option for environments which can be quickly setup and torn down for Proof of Concept / evaluation / testing etc
One downside is that the AWS VPC doesn't support multicast - not a major problem for some application stacks (e.g. Oracle Coherence can use Well Known addresses) but one interesting alternative I'm looking at is Cohesive FT's VPN Cubed - which provides an overlay network.
One of the most significant advantages of this approach is the cost - several hours of usage last night was only a couple of dollars ...