It isn't useful because I always eyeball the range, anyway. If I'm in target practice, sure I can stand still and hold my aim steady and adjust, but when I'm playing HO? Man, even on the novice servers I'm on, people are going to be chasing me and shooting at me and I can't just sit there if I want to be at all useful.
And because there aren't any actual numbers for range (200m, 300m, 400m, etc) next to the reticule, the hash marks are pretty much useless.