I found transformational grammar very frustrating in many ways. But the biggest problem for me was that I can't see spatial relationships in my head. I can create them on paper, and evaluate them as drawn, but I have to see each step on the page before I can assess it. So when I had to create transformative diagrams, I couldn't know how much room on the page I'd need, and where, until I drew it. I personally killed more trees that semester than in the rest of my life!

I don't think I'd find it useful for teaching high school English, either; but I found it very informative for teaching non-native speakers.