merlyn,
From my experience on #perl (Freenode), my biggest explanation for "on-line" documentation is the ability to search for what you are looking for. It doesn't help to have the documentation locally if you don't know what document you are looking for.

Personally, I don't have any trouble using perldoc perltoc and perldoc -q "question" to help find what I want, but I have seen where the search function helped others. Admittedly, I have not played with my local documentation all that much to determine how easy/hard it would be to set up similar local functionality.