My immediate question is how easy it would be to keep your Chef recipes in source control somewhere and have equally easy one click deployment to both AWS and to a local Vagrant development box. We currently have a similar environment set up with puppet and it makes testing sysadmin stuff pretty awesome.
Edit: already finding holes - can't deploy to cluster compute instances (a deal breaker) and deployment seems rather slow (15 minutes to deploy from scratch versus about 8 with normal puppet) :(