I have been continuing to evaluate OpenCart. One of the reasons OpenCart was selected was for its multi-store capability. I would say they have not finished implementing the multi-store capability yet. If you only use what is built into OpenCart and do not directly update the MySQL tables, the multi-store setup is incomplete. You can define multiple stores and define what inventory is available in each store, but that is the extent of what you can do. You cannot define a separate payment processor for each store or define different shipping methods for each store. If you review the MySQL table for the settings, they do support defining things separately for each store, but the front-end has not been defined for it. There is an article in the forums which explains the problem. There is an independently developed plug-in developed called Multi 201 which does provide this capability that is available for $50 AUD. If you are going to be using multiple stores, this plug-in is a necessity.
Edit – 1/25/2015: Found another problem with the multi-store setup in OpenCart. If a customer registers for one store, they just registered in all stores. I think this is a mistake in design. I don’t know of a work-around for this yet.