It's tough to say as everything is relative. I found that for me it depended on the section: organic on the real DAT was much easier and more general than Kaplan, and Kaplan's general chemistry required a bit more number crunching than the real DAT and included more definition style questions. Like others have said, the biology section is a bit more challenging because the questions are pulled from a diverse pool of topics (I studied my class notes and used Exam Krackers for this section). Kaplan's PAT is easier than the actual thing and the RC section on DAT seemed a bit easier than Kaplan. One week before I wrote the DAT I went to Kaplan's site and took their free online exam. It is shorter than the actual thing (the science portions are full length), though I thought that it was closer to the DAT as far as level of difficulty, types of questions, etc. than the exam on the bluebook CD or those on Topscore. In regards to score improvement, some sections I consistently scored the same on while others I had up to a six point improvement on my Kaplan score. Use Kaplan to target your weak areas, focus your study efforts on them, and don't despair if your scores fall short of your ideal.