Yes I do, and greatly prefer it. Just as the written word is more readable in a proportional font, code is too. And more of it fits on the screen!
The only thing that doesn't work in a proportional font is column alignment tricks. (Basic indentation works fine.) That problem is easy to solve by not using column alignment at all. I find code easier to read and much easier to maintain when it doesn't use column alignment. When reading someone else's code that does use column alignment, I just switch to a monospaced font for that file.
If you're heavy into column alignment styles as in the examples from that comment, then a proportional font won't be for you. But if not, give it a try. It may seem strange at first but give yourself a chance to get used to it. You may find you like it, and if not, no harm done.
The only thing that doesn't work in a proportional font is column alignment tricks. (Basic indentation works fine.) That problem is easy to solve by not using column alignment at all. I find code easier to read and much easier to maintain when it doesn't use column alignment. When reading someone else's code that does use column alignment, I just switch to a monospaced font for that file.
I wrote on this at more length here:
http://news.ycombinator.com/item?id=4625340
If you're heavy into column alignment styles as in the examples from that comment, then a proportional font won't be for you. But if not, give it a try. It may seem strange at first but give yourself a chance to get used to it. You may find you like it, and if not, no harm done.