It seems to be the only unique feature though. Any LLM can summarize things for me or make bullet points.

If you have a corpus of documents you are working with (say thousands of pages of related standards docs), Notebook can be handy for doing targeted summaries of aspects of the docs with pointers back into the actual docs to the relevant source material. That's something I end up needing a lot (I've never used the podcast feature) and so it feels very differentiated to me...

The one other unique thing I use from them is the interactive mind maps. Like a table of contents on steroids