I don't think they're that much different than the real thing. I took the DAT yesterday, you be the judge:
AA/BIO/GC/OC/PAT/QR/RC/TS
Topscore 1: 19/17/19/16/19/18/23/18
Topscore 2: 21/19/18 (only took sciences)
Topscore 3: 21/19/18/28/21/21/20/20
Actual DAT: 21/23/21/20/22/18/25/22
Yes the kaplan subject tests are probably more difficult than the actual DAT, but its important to take them so that you have a good foundation for the actual test because you never know what you're going to get. Take my OC scores for example (16,18,28,20) now that's a pretty big variance. I only did 2 of the QR subject tests & didn't do the rest of them b/c I didn't think they were very representative of the real thing. I would suggest getting a bunch of practice tests & just doing the QR section for practice. You really have to work on your speed. I had to answer C for the last 7 Q's. I wouldn't recommend doing too many practice tests (>4) for anything other than QR, unless you have time because I think time could be better spent reviewing rather than finding out what you don't know, over & over again. There was a lot of algebra & quite a few word problems on my test. I just looked at Barron's & I think their QR practice tests look somewhat similar. I rememeber especially when I reviewed organic I got pretty scared b/c I barely remembered it (took it 2 years ago), but after reading Kaplan & reviewing it, you will feel much more confident. I reviewed organic twice & did the flashcards. For the last 5 days before my test I didn't leave my house & spent the whole day studing, usually until 5am (I study better at night). The last day I relaxed by the pool all day (God I love Florida!) & got a nice sunburn. Usually I'm a big crammer the night before, but I'm really happy I didn't. I went to bed at 11 & slept in until 10am. I looked at the kaplan book before the test, but wished I didn't because all it did was make me nervous. I felt like I didn't get anything out of it. Anyway, good luck & make sure you set your date because I couldn't bring myself to study until I had.