i see no use in 4 wire and just did a house with two outlets on a three way in two different areas. dont see the point, when 3 wire works fine. Did as Dennis described, which is the only way i ever run a 3 way, if i can help it. All switches now installed in WA have to have a neutral unless one can be added easily later (run in conduit or fished in). which sounds kinda weird, but whadda i know? But it makes it soooo much easier for me to go into a house to trim out when there are NO dead end three wires in a box.