Great site, but one request: Please make the up/down keyboard arrows switch to the prev/next font (rather than just scrolling the list of fonts). That way I could keep my eyes on the code window to really feel the change.
Currently, having to visually bounce from code window to font selection window and back slows me down and makes it harder for me to compare fonts.
I think it would also be good to mark them as you look down the list, then filter the list and work down it again, marking more until you are left with just one.
Yes, something this would be very useful for actually comparing the fonts. Google Web Fonts has something similar, you can select a bunch of fonts from the long list, that you like from first glances, and then compare only that selection with sample texts.
For this list of programming fonts, I could first select (mark) a bunch that just match my general taste (shape, weight, x-height). Then I would be able to easily switch between my selection/shortlist to inspect more detailed differences such as how numbers are aligned with respect to brackets and operators, or whatever.
Currently it's a bit hard to do if you have to keep a mental shortlist of fonts you like enough for further inspection, to remember which ones to check back on (especially if you see some names for the first time).
Regardless, it's a really cool site, great resource, and already the comparing mechanism is pretty nice!
Currently, having to visually bounce from code window to font selection window and back slows me down and makes it harder for me to compare fonts.