VMware vCenter Converter Standalone provides an option to import Amazon EC2 Windows instances into VMware Workstation, and then importing the Workstation virtual machines to a vSphere host.
via kb.vmware.com
A good start but not there yet, this needs to start happening in flight. Amazon are downright hostile to the idea of moving workloads *out* of EC2, customers need to not give them that luxury and having tools which force the issue is a way of doing that.
This is only the first step in a longer game.
