Lots of my favourite illustrators have a profile there so I thought I might try this myself. To be honest, I haven't bought anything from the website yet so I'm not sure how the art prints will turn out once printed and sent by them. I haven't heard any negative feedback about it, so I suppose the service is fine. Anyway, I think I'll find it out quickly cause I'm planning to buy some prints soon!
To sell you just need to upload your digital files and select how much profit you want to make from the sale. The website will take care of everything else, basically. They will print you send your print for you, easy! I think it's a great opportunity for artists to sell some products without having the problem of invest lots of money way before having earned a cent.