I like this idea but I like the previous version more.. This is too much blue for my taste..Too much KDE (new version) to tell you the truth..while the previous one had more balance in terms of colour..
Technically the title bar and the navbar are not unified, you just colored them the same. It's a nice idea though. Would save a lot of room. Minimal yet functional.
To be honest though I liked the directory explorer pane on the version 3 more. It had the feeling of the Adobe GUI design which is very usable and functional. Simple themes are usually good for functionality, the way they look ( ease of reading text, focusing on a certain section of the window ) and the general style.