OpenStack has the potential to become the ultimate IaaS multi-vendor glue API, and now that the Foundation is established and a number of large players are committing resources and actual code (VMware, HP, IBM, Rackspace, etc, etc), things are taking shape at an amazing rate.
I'd say yes, embrace the AWS API as a baseline, just to make sure developers can port their applications as seamlessly as possible from AWS to OpenStack and viceversa. Just don't think this has to be all or nothing. Since not every use case can be fulfilled by AWS, I see absolutely nothing wrong with creating brand new APIs and operational models to address the needs of whomever is implementing OpenStack out there, as long as it's clear that using them would make your application incompatible with AWS. For many use cases, that's irrelevant.
Kudos to AWS to having come out with that model, but innovation cannot stop for fear of incompatibilities.