This is a screenshot I took last night of my laptop running Ubuntu MATE 16.10 with MATE 1.14 built exclusively against GTK 3.18.
There have already been improvements made since that screenshot was made. You'll notice that everything is pretty much as it was before, although there are a few features of GTK3 we simply can't work around. For example, you'll notice the buttons in the Shutdown dialogue box are linked. This is the best compromise we can create to keep a traditional feel while integrating with this new button arrangement.