I used to do premium. I agree with others that the threads are less combative because many of the sh*tposters don't have premium. You will also get premium articles/info from the CF team when hot issues arise. I originally did premium during the last round of Campbell speculation. I was very impressed with what Chris and the team were doing.
Last year things got pretty nasty between some folks on the premium side. I finally hit a point where I decided I needed less CF in my life and more time away from the screen. So I cancelled. I still lurk on the free boards and catch a podcast here and there.