Learning emberjs
I am not sure if this is a stackoverflow question or git issue. So I decided to put it on stackoverflow first.
Here is my Jsbin (Open in firefox ..not in chrome as raw.github file is used)
When I click on "<- All Department" in department template which I reached after creating a new department it does navigate back to departments template but the #each does not display the newly added department name in list.
It does show the newly added department on refreshing the browser on /departments
UPDATE
It seems that the .set() method is working but for some reason the new object created is returning the name and ID as undefined. Might be a bug with ember-model perhaps.
The best solution for the moment would be to have 2 save methods, one on the edit controller as you currently do and then adding a different save method for creating a new department.
Here is a jsbin with the New controller added - http://jsbin.com/EVUlOyo/1/edit
End Update
It looks like when you are creating the record it is not setting the name value correctly on the object.
I changed the following -
to -
Here is an updated jsbin also http://jsbin.com/EkEXInO/1/edit
Hope that helps and works for you.