I gave it a spin in test. I will say at first I was not a fan of the reduced UI. But after a few rolls I am coming over to that side. General notes:
I agree that death save and concentration checks are things I would really like to see in the system. Players who like this want to click-roll everything.
Is there a way to close the rolls window after you complete a roll? This is adding extra clicks each roll and if the window is left open it takes up screen space which is counter to the design direction.
Otherwise, great work!