Thanks to all your tips and explanations I have finally made a perfect steak.
The short story is: Sear on the outside. Cool 10 minutes, finish in 250F oven for 10 minutes per inch of thickness (roughly). Perfectly medium-rare from the surface to the center. I have only tried it on hanger steak so far, but the results were fantastic. I am sure the same technique can apply to other cuts with adjustments in timing.
The long story, pictures, etc:
Thanks so much for all your help in this matter. I realize that I am pathologically picky and no cookbook helped me nearly as much as all your advice.