They always have a good selection of affordable commuter grade bikes for sale. Its also a great place to check out if you like working on your own bike but don't necessarily have all the tools or facility to do so. The memberships are pretty cheap.
As for the rest of us, who don't like to get down and dirty with our bikes and would prefer to spend more time riding our bikes than working on them, you might want to go to a real bike shop. Its okay for the occasional tube or bike light purchase but if you frequent the shop, you might be STRONGLY encouraged to buy a membership. I stopped visiting due to this a few years ago and I'm not the only one who would rather pay more elsewhere to avoid being harassed into a membership. If I have to pay a little more for the supplies, I'm okay with that, but I don't want to buy a membership to work on my bike if I'm never going to do so. I would rather pay a mechanic to work on my bike for me so I can spend that time doing things more important to me.
Its also not a great place for high end or high quality items. They're mainly catering to the college/commuter crowd. But if you're looking for a deal! This is the place to go!