6pm is run by Zappos, so their service is great. Returns are easy, and they credit you back in a timely manner. I've ordered some shoes and my agate dress from there.
However, they are not the *same* as Zappos, so you do have to pay for your return shipping. Also, they don't list all the customer reviews, so you have to hunt reviews down on your own. The upside is that their prices are lower, because it's the stuff being blown out.