I've always found GAP jeans to be very durable (as in, they can take a beating and keep on ticking) but they aren't very great in terms of style, fit, or feel. If you get the length for short people (which I do), the inseam tends to be just an inch too short for where I like it to fall on my shoes. As a result, the back of my jeans are constantly riding up and getting stuck in whatever pair of flats I happen to be wearing at the moment. Also, the jeans are rough on your skin and don't feel as pliant and body molding as more pricey jeans. Finally, there isn't much in terms of cut or styling, so you're really just wearing an average jean. Cheap, durable, but average.
I always find Gap jeans fit me perfectly and they are readily available in my size. Color choices are sometimes boring and style is basic, but they are comfortable and long-lasting.