Hey, Osclass pay rocks...
I need to know that after ordering an item from the seller, User will have to pay delivery charges to us to drive that product to buyer from the seller.
please make some functionality that asks for delivery charges and after paying that charge seller should get some Confirmation E-mail type to confirm that product still being sold by him/her.
Hope it will be included in next update!
Moreover, seller functionality is good but additionally we can put a checkbox(just like and show E-mail) to every user when they are posting an ad to our site and after checking that box that ad will have a button of adding directly to cart but ad should be moderated as we have to confirm that seller seriously want to sell product through us.

May it helps!