I thought that the Kaplan CD was quite helpful. If you print out the progress report that came at the end of the test, it can give you a good indication of what you need to improve upon. For instance, I got a 15 on the O chem section of the Kaplan CD test, and then printed out the score report. It told me that I needed to work on reactions, and synthesis, and oxygen and nitrogen compounds. Then I took my o-chem book, and the kaplan MCAT o-chem book, and worked like a sled dog on those things that I needed to. I did that with the other subjects as well. Then, I took the DAT from DAT registration booklet, and did well, but I reviewed the stuff that I messed up on.
When it came time to take the real DAT, I brought, for instance, my 15 from the Kaplan CD Test up to a 20 on the real one. I did well in the other subjects also.
So, that is my advice. Study what you missed, and take the practice DAT from the registration book, and you should do well.
Good Luck,
P-