I installed Win 8.1 Update 1 that became available to TechNet subscribers yesterday on my Lenovo non-touchscreen laptop.
Whereas before I could go to the Metro UI start a metro program, then suspend it by dragging the window to the bottom of the screen, and then I would return to the Metro UI start screen.
Now if I go to Metro, run a metro app, then close the app, I get kicked back to the traditional desktop.
The behavior before Update 1 was such that I could stay in Metro after closing a Metro app. Now no matter what I do, including unchecking the "when I sign in or close all apps on a screen, go to the desktop instead of start" in the taskbar properties, I get kicked back to the desktop.
Unless this is a bug, I suppose now this is a new "feature" for Win 8.1 update 1.
