My colleagues think I'm raving mad, because I tried programming with proportional fonts for a year. The result is that I don't want to go back. I really like it.

It all started when I read the book "GUI, webontwerp, psychologie en human efficiency" from Leonard Verhoef (sorry available in Dutch only), and found out that proportional fonts can be read 14% faster than fixed width fonts (Campbell et al 1981; Beldie et al 1983).

If you never tried it before, please try it for a couple of weeks. You might like it too.

Here is a piece of code from Durus, a great transactional persistent object system for Python.

Fixed width Monaco 10pt

Proportional Helvetica Neue 12pt

The fixed width example is a little to wide for posterous. Text in a fixed width font is usually wider than the same text in a proportional font. This is one of the reasons why texts in reads faster. You have more text in an eye fixation. Another reason why it makes reading easier is that the small variations in word width makes word recognition easier. Unlike words in a fixed width font, where all 4 letter words have the same width. All this together allows you to read, and understand, your code faster.