I have sold (once, never again) and bought a good amount of times. I would have to say, as far as selling goes, don't bother. Id rather give the clothes to somebody in need than get pennies on the dollar from them.
When you buy clothes from them, I believe you have to be very careful as they use the manuf. Price and not what the store sells it for. So, in reality you're not really saving what they make it out to be. All the clothes I have bought have been in VERY good condition. My biggest complaint is they codes that NEVER seem to work for me!