Shopping cart is a very nice feature that we think about.
The idea is to add a Cook functionality that store in sessions object, some values and be able to get them afterward. But, for the moment it is not well defined and can but difficult to configure for the user.
Same idea for Rating and commenting, it requires a foreign table structure.
Theses functionalities are for the future, for now, we keep working on extending simple tables functionalities and rendering.
For exlusive information, we are preparing (for soon) a nested hierarchical system. This functionality will be able to manage unlimited levels of recusive tree. A quite complicated code structure when you have to implement by yourself, the right, left, level, alias, pattern, path... fields and manage them.
You can see how is working the categories table of Joomla to undersand better.
It is a choice to do not merge your component categories with Joomla categories.