So... I thought that the altius exams were great in that they had really good explanations of the answers, and were representative of the more difficult passages in the actual exam. That being said, I really do believe that the overall tests were harder than the actual exam, and certainly harder than the FLEs. I got 4 pts below my goal score (8 below my actual) less than 2 weeks before my test date, after I had been consistently doing well on the AAMC FLEs. Moral of the story: good tests but the scoring is wack, don't let it demoralize you. Use only the AAMC tests as a score predictor.
Also, their CARS is weird, I don't think the rationale for some of their answers is the same as AAMC (but is any 3rd party really?)