Order Management

This looks like an interesting cart.

I would like to suggest that you build order management as a plug in or module (not sure which term you use).  The reason I say this is because I prefer to use a central order management tool that is part of my back-office operations.  There are many tools out there that do this like Mailware, Fishbowl Inventory, StoneEdge, etc.  All of them are designed to "truly" track inventory and handle order fulfillment such as pick lists, printing labels, etc.  They also pass accounting data to Quickbooks.

IMO, it's better to integrate with one of these tools than try building all the sophisticated logic of a back-office ERP type system.  Plus, integrating with one of these tools lets you have multiple stores... or multi-channel operations as they call it.

For those who do not have such advanced needs, a simple module or plug in that handles some order management seems fine.  But in general, I would like to see a cart with more emphasis on merchandising and promotions.  Leave the order management to those systems that already do it well.