In the latest revisions (5043) some changes were made to the 3D Viewer, some may like it, others don’t. I’m half in one side and half in the other. Here’s a comparison:
What I really don’t like is that the new color fade effect makes some surfaces appear a little bit rounded instead of rectangular.
I kinda like the new version better.
(And comparing to the 2013 bzr4022, it is night and day!)
Just for the info, in the last version (5059) the rendering options became configurable under Preferences>Render Options menu, you can choose to render or not whatever they call “smooth normals” giving rounder appearance.