We are working with a rather large model in a EF 6.1 code first setup and we are using ints for entity ids.
Unfortunately, this is not as typesafe as we would like, sinc
I was not even familiar with this usage, but did a little digging and even the EF team says it's do-able. From their initial blog post on enum support in EF, this is listed:
Enums as keys In addition, properties of enum types can participate in the definition of primary keys, unique constraints and foreign keys, as well as take part in concurrency control checks, and have declared default values.
source: http://blogs.msdn.com/b/efdesign/archive/2011/06/29/enumeration-support-in-entity-framework.aspx
I have not ever done this myself, but that quote gives me confidence. So it's possible, but as L-Three suggests: really consider if it's what you want (pros & cons .. but sounds like you have already done that) and test test test!