If you use a CMS to build something of any complexity, you will almost inevitably wind up writing some custom code for it. In that case, I think the most important thing, much more important than what language the developers chose, is how extensible and well-documented it actually is.
We are a .NET shop, we'd love to use Django, Drupal, etc. But does that also mean we need a dedicated Python resource to support these CMS'?
Or could we use these CMS' out of the box?
Or would we just be better off with a .NET CMS like Umbraco or Orchid?