Rendering in the 3D-View is smooth and fast as long as the loaded surface is with default properties (color white). As soon as the color property is changed to an arbitrary other color rendering considerably slows down and is snatchy.

To reproduce start extApp or SandboxApp load a bigger surface (e.g. "/home/gergel/Austausch/Surface of bronchialtree Dilated.stl"), take a look at the rendering speed in the 3D-View, then change the color via DataManager and wait for rendering to finish after the changes...