I think some of you guys are missing the point of a tinted final coat. It is not to highlight imperfections, divots, or bubbles. It is to simply show you where you still need to sand so you don't end up having to re-sand the whole room or so you don't over sand a particular area.
As to finding out if my mud is sanded smooth, I don't rely on my eyes. I run my hand along the joint and can quickly tell if it is a go or a no go. I don't rely on any special lighting or anything, generally because I can't see do to all the dust in my contact lens!