Coming to Django, if you want to do auth via email instead of username, you are out of batteries. I say this criticism as a fan of both Django and Rails.
i was astounded how much manual code is needed: http://jeffthomas.xyz/many-to-many-relationships-in-rails
Edit: problem is that when starting a new project people often miss those 20 loc - as well as not noticing the documented best practices for accessing the user...