Shows fine, but the Thing is as many apps got optimized to use external displays as projectors (PDF Expert for instance), sometimes you cannot see nor use there cursor. Also, for every other single app, there’s only mirroring, not extension of desktops.
Second point to take into consideration is that Magic Mouse gestures to move between spaces/mission control and home screen do not work. You’ve got to click and hold. It’s definitely better suited to trackpad than mouse.
Third, there’s still the problem of different aspect ratios and weird cropping when using external displays.
That said, it’s most certainly going in the right direction!