Far be it for me to knock Leica - I love them dearly and my desire to won one is probably unhealthy in its proportions...
The F3's have very bright, 100% coverage viewfinders - one of their best features. Also, changeable screens to suit your focusing needs.
And there are more than a few Nikkor lenses that I challange anyone to imperically prove inferior to their Leica equivalents, awesome as those are.
Their film advance is like a swiss watch. They are an SLR. They have mirrors. They all do that, SLR's... with their silly mirrors and such... but at least you have MLU if it bothers you so much.
There is no substitute for a rangefinder, and a Leica is pretty much the gold standard in that field. But there is also no substitute for a good SLR - and the F3 is one of the greats!
Comparing a Leica RF to a Nikon SLR is a bit apple-orangy in nature. I doubt the Lieca SLR's have much of an edge on the Nikons when you look at it very objectively.
And I am a Canon guy...
PS What is easier (and quicker) to focus than a rangefinder??? Me confused now... me go sleep.