I introduced Django to a company fitting "they're big (Fortune 100)"
I can tell you the single biggest win for the framework. Clear separation of the presentation layer from the rest of development. Designers were able to work within Django templates with no problem and very minimal training.
I don't have enterprise experience with Django but per your second remark, I couldn't agree more. The templating approach using extends/blocks is a breath of fresh air over PHP stuff I used in the past like Smarty.
To put some numbers behind that, in about ~60 days I've overhauled the user interface about 3 or 4 times without impacting the developers. There's no way I could have imagined doing that in the past without causing a big mess. It's great to be able to have this type of flexibility, the hardest thing I've found about UI/UX is making changes after you felt what was wrong about it.
Toppcloud is presently Rackspace-only and Rubber is AWS-only, but they both intend to be multi-service. Rubber seems a lot further along, I'm using it for a customer project I'm working on right now. Having written a project for AppEngine, I don't think either is very much like it -- more a way of getting rid of customized disk images and integrating the bootstrapping scripts with the deploy scripts.
Toppcloud is riding on top of libcloud and should in theory work with anything libcloud supports. Rackspace is currently the only tested environment though.
I can tell you the single biggest win for the framework. Clear separation of the presentation layer from the rest of development. Designers were able to work within Django templates with no problem and very minimal training.