I find the biggest difference between using an SLR or TLR and a rangefinder is the way I see things through the viewfinder. The image on the ground glass, surrounded by darkness, altered, separated from reality, leads me in a different direction to that I get seeing through a direct viewfinder, plain and clear, more directly connected to everything going on around me - I often keep both eyes open.

That's come out as sounding pretentious - I have failed to put an abstract concept that I see clearly into words of similar clarity.

Well, there you go.