QTreeView has a few style issues on Windows.

Selected items are tinted blue. This should not happen on Windows' Aero theme.
The selected background should extend to the tree decorations on Windows' Aero theme.
The expand/unexpand arrows should be hidden by a fade animation when the mouse cursor is not over the tree view and the tree view is not focused.
The wrong header resizing cursor is used.
The Tahoma font is used instead of the system font at occasions. This seems to be a more general problem affecting other widgets.