Please, please, please (is that enough "pleases"?) fix the contrast issue that exists in the tabs for other designs that are currently open at the top of the screen (other than the one currently on the screen).
The contrast between the two blues used is insufficient to make it easily readable, I'm getting fed up of having to squint to see which tab is the one I want to switch to.
This is by far and away the biggest problem for me with the new UI, otherwise I like it.