I've been using django-compress and I'm happy with it, especially because I can specify the back-end compressor (YUI works best with my JS for example).
I will probably consider switching to django_compressor in the future, but it's too low priority atm.
I would also point out that django-media-bundler has one feature the others don't... automatic building of image sprites. I haven't used it live, so I'm not sure how well it is implemented but that's pretty neat. You can use it just for the sprites and leave css/js for one of the other compressors.