I use Django. The main reason for me is the automatic administration generation. What this means is that I create model objects, and Django tools generate SQL DDL for me -- I apply that to my database and Django has a fully generated Adminstration website for me to perform CRUD operations on that data. It chooses good controls based on the types, has search, etc. If I want to tweak the admin, there are classes I can create to do that.
Django has a lot of other great benefits (simple templating language, uses python, easy to host, etc), but the admin is the reason I chose it over RoR.
