Well that looks nice 
I do have some thoughts about that:
- I do like the idea of moving the formatting bar above the title
- Probably the position of the formatting bar could be an option
- There was already a discussion, that some people (including me) prefere to have the option to hide the sidebars completely
- Maybe you could handle the creation of a notebook or a note similar to the tags and put the plus behind the "All Notebooks" or the "Meetings"
- I would prefer to have the search bar in a easy reachable place
- I don't see a use in the very small sidebar as you can't read anything or?
Over all this is very different from the current UI. I like it but there is a very big community and there will be those who don't like such big changes.