And, if you look closely, you will see that the admin controller is gone. In its place is a products controller. It is a baby step, I'll admit. But expect to see more.
Hmmm, I'm not sure that mixing admin actions with publicly accessible actions in the same controller is a good practice. We were talking about that in another thread.
For a model like Product, there is no problem, as the admin and public actions are separate. Problems can arise with the Order model for instance. I wouldn't put admin actions inside the public order controller, it could be very dangerous and we could create a security/fraud if we forget to perform a credential check.
I am currently working on my ecommerce app therefore I am running into these issues.
The advantage of having a admin/orders_controller is that you simply put a global before_filter at the top of the controller, and you're safe.