I didn't start to "feel" my weight loss until I had lost about 15 pounds, but people started saying things like "Holy crap, have you lost weight?!" at around 10 pounds.
But recently it's hit me all at once that, hey, I've lost weight. And not only that, I must be losing inches too (although I really don't know how many, as I never measured myself.) Everything is too big. The knee socks I got for Christmas (that I could only pull up mid-calf) now go all the way to my knees, without cutting off my circulation. My bras all got too big.
I keep thinking that it's conceited to say, or even think, but you know, I'm pretty proud of myself. And even if it takes me a very long time to get to my goal weight, I've changed the way I eat and the way I live, and that's the most important part to me.