I couldn't really tell you the exact time/day/weight when I first noticed a difference, but by now I definitely do, especially when I look at before pictures. I remember once, around 180 lbs, I was looking in the mirror and not really seeing a difference, until I looked at a before picture. Then I thought, "Oh, well maybe there IS a difference!"
It's hard when you see yourself everyday, but hearing there's a difference from other people, watching your pant size shrink, your inches shrink, the number on the scale shrink, definitely helps. I also look at my thighs or my arms sometimes and think there's absolutely no difference at all, but if I feel them, I can tell for sure.