I took the DAT last year (11/07) and I bombed the math (16), not because it was hard, but because I never got used to the "timing." I think you have to answer 45 questions in 40 minutes (or 40 questions in 45 mins). Anyone who has taken the DAT will tell you that the toughest thing about the QR section is the timing.
I hardly studied for the math because the material was so easy. But it sneaked up on me because I didn't get used to the "timing." On the actual exam, I left about 15 questions unanswered because I never got to them.
I used Top Score to study for the DAT. In terms of difficulty level, Top Score was on par with the actual. I only wish I had practiced this section more.
Hope that helps. Good luck studying!