Topscore was nice. What I scored on topscore was what I got on the real thing.
My recommendation is to take kaplan first of course, then when you are feeling good about it, buy topscore for polishing up loose ends.
It worked for me.
Oh, my number one pet peeve was when people would say they were pulling 23's-24's-25's on these practice tests, well they were taking them over and over to get that score. So in short, whatever you buy, treat it like its the real test and take it once that way, then review the hell out of it afterwards. But don't over-inflate your hopes by taking the same test 15 times and thinking that score will be your DAT score. It doesn't work that way.