dof is exaggerated. normally, if the camera's focus is more than, say, 50-100 meters away, more distant objects are only slightly blurred. besides, on your shots there's a distinct division between non-blurred, blurred and object in-between. i'm not sure if you can completely overcome this using Shade-C's built-in dof, but some tweaking would definately improve the overal look of the shots.

looks like the sun is hidden in the clouds(pale colours, no shadows) - it means that the difference between materials' ambient and diffuse colours should be a lot smaller than now.

on the other hand, the colors are excellent and fit the scene and mood really well.

overall impression - good, but it feels a bit empty(which is ok for a desert i suppose )