Option for Product Add On description to show as a hover box
We love Product Add Ons! They are quite effective for upsells. Unfortunately if you add a descriptions to add ons it has the tendency to push the add to cart button far down the page and generally mess with theme layout. I propose that you add an option when creating the add on description for it to show as a hover box (a.k.a. a tool tip). Having a description tool tip next to an option is a widespread UI convention and would give the opportunity to advertise the benefit of a particular add on without cluttering the product page.