I only did the science, PAT and only read the passages of RC (didn't really answer the questions), so I will give you my best opinion.
I got 17, 18, 18 on my achiever PAT and a 23 on the real thing. Every aspect except pattern folding was much simpler on the real thing. Pattern folding I felt was comparable to achiever, but with better graphics and slightly fewer shaded figures.
My scores on the sciences went up a few points on the real thing from my achiever scores, but I really can't say that achiever was representative of the sciences on the DAT. The calculations were much simpler on GC (not too many to begin with), more conceptually based than achiever too. The OC section only had very, very basic reactions. I can't remember achiever's OC questions to be honest, but I got a few spectroscopy questions on the real test that I don't remember achiever testing on. They were still pretty basic. Bio had many more application type questions where you have to understand the underlying concept. Such as "if drug X inhibits the formation of Y, then how would you expect it to affect Z." If I recall correctly, most of achiever's bio questions were fact recollection, which only composed maybe 40-50% of my DAT bio section. They weren't as obscure as achiever, but probably on par with some of destroyer's questions. Don't worry about achiever's RC, it is complete junk in my opinion. I only read the passages to make sure my timing some reasonable, and never answered the questions. YOu will be surprised how much simpler the real RC is compared to achiever. I didn't study for QR so I can't provide info there, sorry.