Just discovered RAML - very interesting!
A few initial comments:
(1) A lot of RESTful APIs use accept headers to express version instead of having it incorporated in the uri/path. I suggest this option be provided in the spec. See http://stackoverflow.com/questions/389169/best-practices-for-api-versioning
(2) Please consider using “Path Param” instead of uriParam, since it aligns better with JAX-RS.
(3) How can one extend the language to support other constructs, like RBAC security authorization statements? I think this is a must have to be able to provide extensions to the expressions, not just for security but for anything.