This place is amazing! The building is huge and the variety of fabrics available can't be beat. They've also got lots of sewing accessories and other odds and ends, and all of them are at unbeatable prices. Shopping in there is like a fun scavenger hunt and you have to search to find what you're looking for, so don't expect to drop in for a quick visit. I'm always here a few hours at a minimum.
The only downsides are that the building is really hot and sweaty in the summer, and that sometimes it can be hard to find what you need. Even despite that, SAS is my favorite fabric store in the valley.