The chemistry made me want to bang my head on a desk until my forehead was bleeding. I'm five years out of high school and haven't touched chemistry since 11th grade; there was no way I could possibly learn all of that stuff again.
I didn't like that the study guide tests were so different from the real tests (there were more anatomy questions and questions actually relating to nursing such as things about reading blood pressures etc), but then again I did horribly on my practice tests and well on the real thing, so maybe it was better in my case.
I guessed on a lot of the chem, though. Educated guesses, but still guesses.
As far as scoring goes, my school just takes the top 128 raw scores of the people who met the prereqs to test. Every school is different.