I think season 6 is one I liked a lot more in retrospect. (I think that actually applies to all the later seasons. I enjoyed doing them at a readthrough more than the earlier seasons, even though I enjoyed the earlier seasons more on first watching.) I think I liked the overall structure of the series, and many of the individual episodes, but when I first watched it, I was constantly thrown out by seeing characters make decisions that didn't seem to make sense. (Jonathon not angsting earlier about being horrible to Buffy. Willow suddenly getting so much more addicted to magic and suddenly killing people, etc.) Those all make more sense from the point of view of the larger plot, but often made me go "huh? that character just wouldn't do that" at the particular point where they happened.