Thanks for taking the time to work on this mock-up! We all want to make OpenShot as pretty and usable as possible. My initial feelings on this mock-up are mixed though. I really like the changes to the timeline (bottom of the screen), especially the dark ruler and stylish transition. I am not crazy about the transitions and effects boxes always visible, or the lack of a menu bar at the top.
One of the things that sets OpenShot apart from all other video editors on Linux is the non-intimidating look of the interface. It has very few things to interact with by default, and users have really responded positively. The biggest negative we hear is the icon themes clash with their Gnome themes, and the timeline is too shiny blue (also clashing).
So, this mock-up addresses the biggest complaints and gives us some new ideas about how the layout "could" look.
Another thought I had after seeing this mock-up was about the way we build this screen behind the scenes. It would be cool if a theme (or some preferences) could affect where each panel is attached. Maybe the user could quickly change a few preferences and have a screen very similar to this mock-up, with some panels always visible, no menu bar, etc... This is an interesting idea, and one that would allow power users to really configure their screen, while new users could just live with the super simple default layout. Just a thought. =)