It has its merits. I think it does use space well. It would be silly if I said it was bad, because it works for some people, obviously.
My main criticism was that it relied a lot on search (which I basically never want to use), and it had an annoying habit of hiding things. I really hate it when UI's get super clever and try to guess what's useful to me, I'd rather things just stay in one place and I'll remember where it is. Whenever UI's try to "adapt" to users, I just find it makes them unpredictable, and efficiency is more about predictability than anything else.
My main criticism was that it relied a lot on search (which I basically never want to use), and it had an annoying habit of hiding things. I really hate it when UI's get super clever and try to guess what's useful to me, I'd rather things just stay in one place and I'll remember where it is. Whenever UI's try to "adapt" to users, I just find it makes them unpredictable, and efficiency is more about predictability than anything else.