I think the topical tests were good challenging sections to take after you did all the review material and some FL's already, so you can go back and see if you have any weaknesses popping up, but also to refine and keep your skills in material that you may have gone over two or three months ago. Are they tough? Yes, but would you rather be practicing difficult material and doing decent, and then coming to the MCAT and not be shocked by the difficulty, or would you rather take easy practice that you ace and then have one or two bizarre mcat passages ruin knock you off your game?
A lot of it though, especially physics and chem, are very math intensive. More so than the AAMC FLs or the actual MCAT, but if you use these for practice I think it helps you understand the concepts a bit more and solidify the math/theory knowledge of the topics. If you can integrate it into your thinking and language than questions will become clearer. Like that solubility question someone posted in another thread. Sure, its a straight up math question and one that probably would come up on a kaplan FL or topical but if you understand the theory behind the math you would see that when the compound gets dissolved there's two hydroxyl ions per molecule so the solution should be basic.
What I'm trying to say is the more practice you can do the better, and the more challenging it is, the more you'll learn.
