I've tried several of them and they are all glitchy. I cant afford to waste time. My time is all I really have...till its gone.
Inkfrog. Sixbit. Auction Sage. Auctiva. Vendio. They all have problems; uploading, saving, getting the shipping right, buttons that don't function, ugly templates, printing labels, error messages et cetera!
If your not an EVERYDAY seller or if you sell UNIQUE items. Save your money. Put all your boilerplate copy in an RTF file and work directly with eBay. It might take you longer initially but at least you won't be pulling ALL your hair out!