I've been using Cubase Pro 9 for about a day now, and I'm really impressed with the user interface redesign. Much more of what I need is right there in the project window and a lot less mouse work is needed to get to various features I want to use.
I started with Cubase 7, and it seems clear to me that Steinberg is steadily evolving the user interface towards being useful and functional on machines like tablets and laptops. Since I'm using Cubase on a Surface 3 tablet, the user interface improvements are really helping me.
So far I've run into two minor glitches with version 9, neither of which got in my way for very long. I'm really pleased with Cubase Pro 9. And as someone with user interface design expertise, I'd like to compliment Steinberg on the excellent job they've done.