This new admin is absolutely stunning!
The only thing I see that I would like to have back, is that when I roll my mouse over the left main admin menu links, I can't see the sub-links modal popup. That forces me to have to click the parent item, wait for it to load, and then go into the sub-menu item. It's just a waste of time and a click when you are in a hurry and already know where you want to go.
Imho other than that, this admin is a huge improvement.