Programming in Python, where whitespace is syntactically significant, with a proportional font, seems to be volunteering for an unnecessary burden. Reasonable people may differ.

The only mitigating factor would be that the spaces at the left margin all (presumably) have the same width.

Another proportional font using python programmer here. All significant white space is in the left margin and all has the same width, so not a problem at all.

And those are the only spaces that are significant in Python. Indentation works fine in proportional fonts, just like it does in monospaced fonts. The only thing that doesn't work is columnar alignment after the indentation, and that wouldn't be significant in Python anyway.

Proportional fonts seem to work for me in ST2 (http://i.imgur.com/ZLZWP.png) I just put this into the config:

    "font_face": "Verdana"

Though I may be missing something.

You're not missing anything. I'm using Georgia in ST2 via the same font_face setting you're using. Works great!

No, you aren't. I tried something like that in the past and it didn't seem to work. No idea why now!

In fact, I'm pretty sure if you put an invalid font name in you get a default proportional font.