Which one do you use? I love proportional font but find most of them not suitable for code. Input Serif is the only proportional programming font I can find but it looks too old school.
Georgia, modified to put a slash through the zero, and a small horizontal line, like a serif, on the l. Theory being, letters in serif fonts are easier to distinguish since visually they're more different from each other. Same reason the body text of books uses something like Times New Roman, only headings use a sans serif font.
I've been using Verdana for ~10 years. I've tried others but keep coming back to it. It continues to be a very consistent and elegant design for screen.
Try the sans variant, it looks almost indistinguishable from monospace font but more comfortable to read.