The key differentiator of Roads is the ability to comment on audio with audio, however in the initial version you could only comment one level deep.
This was a major rewrite to the codebase because initially the app had two types of audio. Episodes (the main conversation) and comments.
With this update all audio is now considered a Post, and there are several Post types (Root Post, Comment Post, Response Post, etc.). The new setup is much more flexible and will allow for future post types, but more importantly this setup allows for conversations to continue naturally within the context of the audio you listen to.
This was a highly requested feature from several of the early users, and was developed in response to that feedback.