The nice thing about it from our point of view is the ability to keep everything in source control. Granted, you can keep your cron jobs as scripts, but celery+rabbitMQ allows you to keep it all in Python without the extra deployment step. It's not a huge deal, but it does help a bit with maintainability and getting new devs up to speed.
We keep all the deployment stuff in source control anyway. For me, it would just mean shifting it from being declared by salt in the "infrastructure" folder to being written in python in the django folder.
I agree that you should keep the code itself in python, but that can be handled just by making it a management command that gets called by cron.
Sysadmins understand and love cron, too. I think celery reinventing the wheel might make some of them a bit mad.
I never really saw the point of that part of celery anyway. Cron's perfectly adequate on its own (and installed just about everywhere).