4teamwork, kitconcept and other companies already use plone.restapi in production. So we could declare the current version 1.0 at any time. Though, for now I would prefer to keep it in alpha to make it easier for us to make changes and not having to support multiple branches.
One thing that I would really like to see though, to make it easier for people to adopt plone.restapi is a browsable API, comparable to what Django REST framework has:
http://restframework.herokuapp.com/
The Django project did a kickstarter campaign to make this happen...maybe something we should think about as well...