The Gap is great for basics, but most of the time, the clothes are overpriced. So I usually only buy things on the sales racks. Sizing for bottoms is really crazy there too, their pants and skirts are vanity sized and sometimes cut strangely so they don't look good on your body, or at least, my body. It really varies from piece to piece though... Their tops are decent though.
As an American though, I am quite jealous of the Gap's European collections, which appear much more fashion forward than most of the stuff they sell over here.