It just felt like the theme shifted to me. The earlier seasons had a darker touch to it compared to the later seasons. Plus, the earlier seasons didn't look much orangey in Buffy's house. I prefer the high school library and Giles's apartment over The Magic Box. I miss the factory, Angel(us)'s old mansion, and Angel's old apartment(whatever happened to that). Those places were better than Spike's old crypt. I prefer Bangel, Xandelia, Ginny, Woz, and Sprusilla over Briley, Spuffy, Xanya, Tillow, and Wennedy. Even though I have grown to like the Buffy/Dawn sisterhood, I still prefer it if they kept Buffy as an only child considering that's the way it was originally made. It's no fair that we didn't get to see Dawn/Angel/Joyce in the present time.Definitely seasons 1-4, with season 3 being my absolute favorite.
The later seasons have grown on me though over the years, and do contain some of my very favorite episodes.