Shoudn't the goal be the opposite - firm but not terribly fast? I think most greens are too soft, which makes all the angles and strategy (which is supposed to be important) irrelevant. Meanwhile, if they get too fast, then you start to lose pin positions and few architects will design the bold contours that used to be prevalent.
I know a lot of courses that are soft and fast, but from a design perspective, I would much prefer firm and a little slower.
Art,
TEPaul had a practical theory about that.
Now I know that's a contradiction of major proportions, but, essentially his theory was that the superintendent should determine the maximum speed for the greens based on the most severe green, and then use that speed universally.
I like the concept as it's the perfect blend of speed as it relates to contour and slope.
Too many wonderful green contours/slopes have been lost to speed.
Greens are THE unique feature which can most affect play.
Therefore, preservation of wonderfully contoured/sloped greens should be the ultimate goal with speed as the icing on the cake.
As to soft but fast greens, I recall that German Bent or Velvet Bent putted extremely fast even though the greens were fairly soft.