Interestingly enough, I used a buddies snap on digital torque wrench on a head today, which has an angle meter built in in 1 degree increments. He wanted me to try it out over the traditional angle meter, so I figured what the heck. It tells you the angle you are at, and beeps when you hit the preset spot...in this case 90 degrees. After you remove the pressure at 90 degrees, it tells you the torque as well. The torques were different on every nut. IIRC the 1st 90 degree swing was anywhere from 35-45ft/lbs, and the second was anywhere from 65-72ft/lbs.
Makes me question the validity of the 90 degree method, though that is what I have used on the gabillion heads i have R&R'd and never had an issue. I figured the tolerances would be much closer than that.