Boy, I think "size down" is all relative. Gap isn't quite as bad as Old Navy, but it seems to me that the jeans vary somewhat pair to pair. They also run pretty big. At other stores, I often wear a 6 or even an 8, but at Gap/Old Navy, I am usually a 4. The jeans do stretch out a little bit, so I buy the smallest size that I can comfortably zip (pretty snug).
I just bought a pair of Gap Perfect Boots--thinking of YLF, I chose the lighter wash! I love them. The wider waistband is very flattering and comfortable, and the fit is nice. I tried on every pair in the store that they had in my size to find the best fit. (The waist was larger on one, one ran a bit smaller overall, etc.)