I agree with everyone above.
Joyce annoyed me so much because of her ignorance and attitude towards Buffy being out late(me having mom problems of my own at the time didn't help). I knew she was only being a good mom, but I was still very annoyed. So when she found out, and she and Buffy seemed to get closer, and open up, I started to like Joyce. It was nice to see a new phase in their relationship.
The season 5 moments, when Joyce had serious talks with Buffy about her desease and Dawn were precious. They really stood out to me. There was a deep connection and it was wonderful to see how Joyce saw and pointed out how Buffy had grown from a girl to a woman. I think I knew that already, but seeing Joyce treat Buffy as a adult really made me realize how far they've both come.