Any potential gotchas or things to be aware of for a newcomer to Django?
You can't process data in templates.  There are a fair number of questions in SO from people trying to do "real" processing in the templates.  The Django template language is -- intentionally -- not JSP or ASP or PHP.  It just does presentation and retrieval of values computed in view functions.
If you can't figure out how to do it in the template, you may be trying to do too much.  Use the view functions as much as possible.
In other words, what did you not know when you started with Django that you wish someone had told you?
I've dabbled some in Django but nothing really serious. However, I'm hoping to change that, and I'm wondering if there's any gotchas/shortcomings/whatever that I need to be aware of as I  go.