I've always liked the extra area view of the .72 finder with a 50mm lens, had and sold, a Leica 1.25x magnifier because of this. It was nice to use with the 90 but for the price thought an extra body in the form of an M3 would be a better 'replacement'. Had a .85 finder for awhile and got to like the larger view even with a 35mm lens, so...
Just bought another to give it second try and am liking it more as I use it. With the newer short throw 50 Summilux (pre-ASPH 46 thread) I have now I feel it increases the focus accuracy, makes for a larger rangefinder patch (especially good with the kids), bigger all over view for composing, and the general easy of focus is giving me more confidence. I like it. The only disadvantage I find now is the thing sticks out and I have adjusted my usual way of holding the camera face-to-camera a bit. Again, especially good with a 90 combined to a .72 finder, even and if you are using it with an M3 would give you a better 1:1 view.