So this actually moves the search bar away from my workspace. I don't use the Reading Pane. (I despise it for a couple of reasons.) This forces me to actually open the message to read it and the message is only marked as read when I open it. This new location feature puts the search bar in an area of the window that I don't regularly look at.. above the ribbon. The only time I look at that part of the window is to exit.
So I am imagine this is a nice improvement for people who use the Reading Pane and probably are annoyed that it truncates the size of the message list and consequentially the search bar... but for me it is a productivity back step. If I didn't use it so much it wouldn't be an issue. But as in 5S, you put those items that you use least farthest away, and those items that you use most the closest. Oh well.