I use Django for my projects and I don't share this opinion on the maturity aspect. Can you explain your statement a bit more? What aspects of Django are immature?
There were plenty of extensions that allowed you to use Selenium with Django, I maintained one of them. Django is fairly conservative about including new features into the core that work well as extensions. And this is something I value a lot.
The time zone support, though, was really overdue.
Not really a fair feature comparison. If db migration wasn't in Rails, ActiveRecord wouldn't work the way it does. You can't say the same about Django's ORM.
Time Zones were added to Rails 2.1 in 2008. selenium-on-rails also debuted in 2008.
Does it not seem strange to you that it took 4 years after Rails for Django to get these features?