Unless things have changed in the meantime, the killer feature of CloudFormation for me is that I don't have to keep track of the state locally. Having to set up tracking of the infra state in Terraform is a huge pain, since it should be stored independently of both the infra code (to allow deploying anything but HEAD) and the infra itself (duh). As long as Terraform doesn't query the existing infra to work out what needs doing I don't want to go back to it.