Main effects on Windows:
* Label in LabelFrame is blue.
* Widget frames turn blue when target by mouse.  (This is especially nice for checkbuttons, where the visible 'frame' is the circle, while the mouse just needs to be inside the invisible actual frame that includes the circle and label.)
* Button flat (I know that we could restore 'old-fashioned' relief with explicit styles) and sometimes larger.
Font sample left-justified instead of centered.  No necessarily bad.

Overall, a slight improvement even on Windows.  We can tweak details when revising individual pages.

The dynamic option menus look out of place, and should be replaced.