One of the workflows that have been added to Inventor is called Model States.  This workflow is not dissimilar to iParts and iAssemblies but even more powerful as all the variations whether you are working in a part or assembly exist in one document.

Because these variations exist in one document and not multiple files like your iParts and iAssemblies, there is no need to be concerned about breaking the links between the files that you create.

This functionality has been requested frequently over the last year or so and I am very happy to see it being introduced into Inventor after extensive testing in the beta sessions.

You can use model states to create your parts or assemblies in different manufacturing stages.  You can have your assemblies have different simplification stages.  This could be useful when working with BIM parts for the Revit guys.  Different product families can be created as well as you can have adjustable or parts in different states.  Maybe a sheet metal part that is bent and then one that is unbent or different states of bent up part.

Each of your model states can contain different dimensions, features components for you bill of materials as well as have different iproperties and parameters.

When creating 2D drawings one can show the different model states that have been created either in the part or assembly.

I spoke about model states been similar to iParts and iAssemblies but all states reside in 1 document.  If you need separate files that need to be managed separately then iParts and iAssemblies are still available in Inventor.