I wouldn't like to wear it when teaching because the shop I teach at like their instructors to use 'standard' scuba gear, especially with open water students. The theory is that they have seen it done one way on the video, but will see it demonstrated another way in the pool. Although when I assisst in open water I wear my lovely little eclipse single tank wing. With the crotch strap it allows me to stay nice and vertical at the surface, something my old custom divers wing never did, I was just pushed onto my face with that.
When I have advanced students, I wear it, because there are very few skills I have to demonstrate, it also allows them to see a different configuration, one that is gaining popularity with all divers, not just techies.
But when we have rescue diver students, I wont wear it, tried it once, they nearly broke my arm trying to get it out of the one piece harness. I explained to them in a real situation, if that sort of problem occured, they should just cut the harness. Even getting myself in and out of the harness in a hurry tends to be tricky.