I've been using my tree stuff on construction jobs, and I like it a lot. If I'm just walking beams or something, I'll use a basic lanyard on my top rear D. If I'm climbing around forms, and having to change position a lot, I use my lower front D with a prusik + rope. I can bring it way in to reduce travel, or take it out to ~12'. It's kind of a manually operated yoyo without the weight or drag. I'm probably violating some rule or another, but it looks good from a distance, and nobody says anything. You have to make sure you can't fall far though. A decent drop on the lower D could mess you up.
edit:
What I also like about the tree lanyard is I can self rescue if I fall off a beam using the fall arrest lanyard. Instead of dangling like a piñata waiting for someone to haul me up, I can toss my tree lanyard over the cable, and climb up it. Not that that's happened so far. It was always one of my fears, especially when my robot still worked, and I was doing it by myself at night. It would take quite awhile for someone to notice I was there, and get me up. I made a trauma strap I kept on that harness so I could hook it up and stand in it in case I went over. Takes weight off your crotch to prevent harness trauma.