I’ll second that my thinking skills have improved, though due to endocrine problems that affect my brain, I’m not sure I’ve seen a noticeable, tangible improvement.
I certainly learned a lot about careful writing, brevity, proof reading and fact checking from my brother and sister Freepers.
Much more than I ever learned in high school or college. One of the best influences on my literary style was National Review on dead tree. I really learned a lot about clear thinking and presentation reading it.