Honestly the one interface should be the AWS API. Eucalyptus has already embraced it and set the tone. OpenStack is partially there but political battles in the community have forced a stalemate.
If you standardize on the lowest common denominator, you lose many of the key features of AWS such as VPC and autoscaling.
If you standardize on the lowest common denominator, you lose many of the key features of AWS such as VPC and autoscaling.