[tim chapman]

When I am playing in a group, no one ever waits on me to pace off putts. Most of the time no one even knows I'm doing that. It is the first order of business when I get to a green. While others are marking their ball or repairing ball marks, I am getting the measurement. I am careful to not step in someones line and am never discourteous in the process.
Many times you have to walk past the hole to get to your ball anyway.
If it is an extremely long putt, I will walk half way.
I would no more guess or estimate the distance anymore than I would when hitting an approach into a green.
As I have told many of my students, "If you're waiting on me, you are backing up" (also it takes me less time to one or two putt than it does for you to three putt).

interesting discussion, for me putting is best as a right brain, creative, intuitive activity in the same way that lobbing someone a golf ball for them to catch is, we don't really need to know how far away they are to do it.
that said, maybe it would all be information going into the super-computer that might be be called upon somewhere down the road - i'm going to give it a try, by mentally noting the distance prior to the usual routine.