It's a good free source of practice passages. There are errors scattered throughout and I wish the format was more similar to MCAT style instead of question by question but I think it's a good place to get extra practice.
I wasn't a huge fan. Definitely good practice but there format was weird with like 2-3 really long paragraphs instead of the usual ~6 shorter paragraphs that you would see with AAMC. I remember one that was just one super long paragraph. But I think their answer explanations are decent and passages can range from easy to challenging so good practice for sure
Overall I think its good practice, but some of their answer choices you will never see in an actual AAMC. For example, AAMC never includes an AC that says "a and b only" or something like that.
I initially had trouble with CARs while I was studying, and greatly improved after I went through all of the Kahn CARs passages. I'd highly recommend them