I've been playing with org-mode column view (org version 6.28trans, fresh from git!) and working my way through the Org manual to try to understand this tool and see what neat tricks I can pick up by using it. Today I have been playing with column view.
Column view by default only shows a single subtree. In order to do column mode over an entire buffer, you have to have text before the first headline, and go there. It seems to me that the usefulness of showing a single subtree is more limited than showing the whole buffer in column view. (This seems to be confirmed by the fact that in Agenda mode, C-c C-x C-c brings up column mode over the whole file.) But as far as I can tell, there's no way to force a whole-buffer approach -- not by a special function, not by invoking with a special argument, and as far as I can tell not by hacking up a simple function (assuming there isn't text already before your first headline).
I guess what I'd like to know is: what am I missing? Do most users only do column view over subtrees? Is column view really only used in agenda view? Do all org users keep text at the top of their files to specify file settings, and just use that? Is there a simple way to column-view a whole file that I'm missing?