By looking at the GIF in helm-org-rifle I remembered reading about variable-pitch fonts on (what I believe to be) your blog. Great content in there, thanks a lot for sharing!

Don't actually have a blog, but I've been thinking about one for some Emacs-related stuff (though it would be feeble compared to the Emacs-related blogs already out there!). I assume you know about Planet Emacs, but if not, planet.emacsen.org. :)

Anyway, about the fonts: I use monospace fonts for code, but I like proportional fonts for Org documents, so I have this in my org-mode hook:

    (buffer-face-set :family (face-attribute 'variable-pitch :family))

Then I use monospace in Org code blocks like this:

    (set-face-font 'org-block-background frame-font)

You could also set that one in the customize interface.