I've been using Django for a lot of projects, but have recently converted to Rails 3 for a personal project.
What I like about Rails is that plugins are mostly pieces of infrastructure, not ready-to-use mini-applications that are hard to customize. And Rack plugins (pieces of middleware, done in a standard/reusable way, contrary to Django's middleware) are just awesome.
I also like about Rails that authentication and admin are not built-in. Lots of plugins available for a quick-and-dirty job anyway.
I also like that defining models and even querying has been abstracted away in different interfaces, and that you can use MongoDB in a similar way as you would use a relational database.
Also, in case you need to decouple the request validations from the models (i.e. forms in Django) without HTML-rendering logic attached (useful at times, but completely getting in your way once you try doing anything complicated); in Rails you can, and it looks and feels cleaner because the field types don't have to be related to stuff you're rendering in the HTML response (i.e. field = forms.MultipleChoiceField(widget=CheckboxSelectMultiple)).
Django is awesome in case you ever thought about using Drupal for a project: much more flexible and dev friendly. But it completely got in my way so many times that I actually thought about writing my own Python web framework; which I shouldn't because people have been working on web-related stuff for the past 20 years.