Overall, achiever is way harder than the actual DAT. My scores on Achiever were like ~16 bio ~18 chem ~18 ochem, although I took them about a month before my DATs so I hadn't studied a ton. TopScore is much more realistic but is still harder, considering I got ~18 bio ~20 chem ~20 ochem.
Bio - Don't waste your time studying a ton for the section. Just like people say, regardless of how much you study you'll get random questions that you won't predict. Just use common sense...the questions weren't nearly as specific as in practice tests.
Chem - I found it to be surprisingly easy. There wasn't much calculation at all and when there was, it was very simple. I'd recommend doing all the Destroyer practice problems and reviewing missed problems in topscore/achiever. Time was not a factor at all in sciences...I rushed at first and had time to check the majority of my answers.
O-Chem - Again, it was really easy. If you know all the reactions in Kaplan blue book you'll be totally fine. A lot of questions were SN1/SN2/E1/E2 and didn't specifically state it. Destroyer helped practice but Kaplan is all you need to do well.
PAT - Achiever is REALLY good practice for this section. I found every section to be easier than achiever except for angle ranking. I had time to look through my entire PAT section a second time which I wasn't expecting. I doubt I missed more than 1 or 2 problems outside the angle ranking.
Reading - Uhhh piano section is brutal apparently. I was getting 23-30 on every prac test. I really thought I did fine on the piano section too but apparently not. My first passage had a LOT of questions asking for tone, inferences, etc. Not very expected but not too bad I thought.
QR - I was getting 22-23 on all prac tests and the QR was the most surprising section in terms of content. There are a lot of wordy problems that take up your time. I was scared of running into difficult probability/permutation/combination questions but didn't see any. It's definitely worth it to totally skip problems that seem really hard. Also, plugging in possible answers is a quick way to avoid wasting time on problems requiring complicated equation sets.
Hope that helps some..
