I had been looking at the API for a while, thinking it would be easy to make a crawlable version of ebay to get some search engine traffic. The problem with this is they have recently changed their setup to use more friendly urls and allow bots to crawl more deeply. And you can imagine how much
PR they have to pass down to these pages!!
http://www.google.co.uk/search?hl=en...ebay.com&meta=
I've sent the new affiliate team a few questions, but if your interested in it I would join the individual tier, which is free and will let you try stuff in their sandbox without having to pay the $250 in advance.
Just watch out for the minimum convertion requirements!