Why separate Add/Edit?

I'd tend to agree with Carlos and while I haven't tried it, it seems like it would be easy to achieve manually. (I think there's been a post or two about this here before). Just pass a page type parameter to the receiving page, and handle the load and submit items based on that. However, wiring up at least one type of component, the multiple select dropdown, is rather different for each type and would probably negate any benefits.