The computer reading to you, and you then put into a fixed speed for the test was very very frustrating for DD. She actually was able to come home after it mimicing the computer's voice with amazing accuracy. She said it was "way to easy, and frustrating, and too S-----L------O------W"(read as a 6 yr old exaggerating slow speed with slow speaking).
After she took the secondary test she reported back that it was much much better because she could read the questions at her own speed and go as fast or slow as she wanted to.
At her school they start using the secondary test for 2nd graders, when they figure the kids can all read well enough to do it on their own. (DD is reading at about gr 5 level, so it was pretty much torture for her to listen to the whole test being read to her.)
She finished the math test yesterday, but there was a crisis at the school

and they gave her the option of finishing it later, but she chose to finish it then, so I'm not sure how well the math grade will reflect any difference between the tests for her, but we'll see.