"It appears that most of the source information that you get from Ancestry lists Ancestry as the REPOSITORY. However, is this really factual?"
When it is your access to the source document, of course it is.
"I was wondering how others enter the repository information."
Easy rule of thumb, whatever you "link" to is the repository for that particular source. Changing every document citation to its original source (e.g. Bureau of the Census) is just not feasible (or necessary). For bloodlines, I will often offer alternatives (with repository designated eg. 1910 United States Federal Census [Internet Archive])...but I'm not dogmatic about that either. They can, however, be useful for non-subscribers.