Hi Scott:
I haven't been in the States since I was working in central Nebraska in 1996, but I never saw LED signals there. Just before that I traveled pretty extensively around Ga, Ala, NC, SC and Fla, and again never saw any.
I've not seen any here in England yet either, but I was in France about two years ago, and noticed LED signals everywhere. As you said, the smart "snap" from one color to the next is what really gets the attention at first.
Many of the normal lights seem to have been converted, but it was hard to see the exact arrangement because they still appear to use a gel or lens of some kind.
Junctions with high suspended lights in France usually have a small repeater set mounted at eye-level for the driver at the front of the line. Just about all of these seem to be LEDs now, consisting of a dozen or so high-intensity LEDs arranged within a 2 to 3 in. dia. circle.
