It will open at a window size of smaller than maximized. On my 1600x1200 screen, this is about half size (though it appears to think it is maximized.) If I click the windowed button at the upper right, it gets even smaller, and knows it's in womdowed mode and not maximized. When I click the maximize button to maximize it, this time it expands to full screen.
It repeats this behavior every time the program is launched. Previous versions remembered the window state, i.e. maximized and displayed correctly at that state on a launch.