I've used BANS and phpBay and personally I like phpBay better. It may be a little more difficult to use than BANS, but I think phpBay has way more customization.
Last time I used BANS, which was before 3.0 came out, the themes they had were crap and I didn't want to waste time making graphics and changing colors to get the site how I wanted it.
Where as with phpBay, you don't have to worry about that since it runs with wordpress and there's tons of wordpress themes to choose from. Way easier to manage as well in my opinion.
I also heard that phpBay is going to support Amazon.