For me, it's too low contrast. Extremely thin, monospaced, light-grey font on a black background just doesn't read nearly as well as well-proportioned proportio

For me, it's too low contrast. Extremely thin, monospaced, light-grey font on a black background just doesn't read nearly as well as well-proportioned proportional dark font on a light background — or, if it must be a dark background, yellow text on dark blue is the most legible. Regular Courier over Courier New could help, too, but ultimately a proportional font directs the eyes more easily.