Just signed up with Allposters.com yesterday. Too early to say anything much except that its very easy to use and install code.
They pay 25% commission and this can rise to as much as 30% if you sell enough stuff.
I'm only testing the water with it at the moment on one website - but in the first 12 hours, with it on just one page, I know 6 people clicked through (no sales yet though); this is very impressive given adsense normally only gets 1-3 clicks per day from this page! I've justed rolled it out to all 400 pages on that particular site (its a fairly low traffic site though, 70 unique a day...) Will give feedback as soon as I can realisticly (a week maybe).