I noticed that some borders have been removed from the builder chrome (the .tco-bar for example) which previously provided some nice separation between the builder and the preview panel. Now the builder blends in more with whatever you’re building, and I’m not sure if that’s a good thing. Going back and forth between this beta and the previous release, I think I like the thicker borders better.
@JvP, there is a slight inset shadow on the live preview to help offset it some, but I will note down your thoughts and hear what others have to say. There was some internal discussion on wanting to clean up some of the extra noise of the interface in different spots, which led to the current iteration it is on. I can certainly hear where you’re coming from though and would be curious to hear the thoughts of others on this if they’ve noticed it or have a preference (knowing we can’t please everyone as I’m sure some will have strong opinions either way 
).