Let's say I have a product page with accessories, and a checkout page. I want to include a another group of accessories that this user can add to cart on their way out. It's a candy aisle, basically. Do you think it would be good to include this candy aisle on the right rail of the checkout page, as long as there are NO LINKS to other pages, only ADD TO CART links? This way, I won't interrupt the checkout process, but it's easy for the user to add more things on their way out? Do you think this setup would hurt conversion in any way?
What about a scenario where it flowed from "Product Page" to "Offer of a better product at a slightly higher price" to "Checkout"? How many people would you lose a conversion to by inserting that Offer?