New Facebook Apps To Promote Ecommerce Stores

I am seeing a trend with Facebook app developments that seems to promote selling physical products on Facebook. I think this is great for ecommerce store owners as they can leverage the millions of  new people joining Facebook every day. Not to mentions the milions of potential customers already there participating in segmented conversations.

I would love to get some feedback from others, what apps are you using and why? I discovered one that I plan to implement called Payvment that is on my to do list. Is anyone using this one in particular? What do you like about it? What do you not like about it? Was it easy to implement?