As of Umbraco 7.7.0, Nested Content is available as a default built-in property-editor. We are no longer actively maintaining the standalone package version of Nested Content.
Nested Content is a new list editing property editor for Umbraco 7+, similar to likes of Embedded Content and Archetype, however Nested Content uses the power of doc types to define the list item blue prints. By using doc types, we get the benefit of an easy / reusable UI we are all familiar with and also get to re-use all the standard data types as our field editors rather than being limited to a subset of “allowed” types.
Nested Content then is probably the last list editor you will need for Umbraco 7+.