I disagree that the topics covered on topscore are not on the real DAT. I am currenly using topscore and find the topics very similar to the listed topics in the dat registration manual. These are the topics on the DAT according to the ADA test writers. In fact, I printed out the topics from topscore and find that nearly every one matches to a topic(s) convered in my registration booklet.
I think that topscore may be a bit harder only because some other people say so, but I don't know that yet. However, if it is a little harder, I see that as a good thing and have used it recently to find some of my weak topics. I have the Kaplan books from Amazon and these books are the same as what you get for the Kaplan course. I am convinced that the Kaplan books are not the level of detail you need to score in the 20's, so I am also using some of by class textbooks. My sister, a dental student now, says that using this combo that includes heavy review from text books is a must.