I missed...
- the interaction between Brenda and Dylan (a couple or not, but preferred them as a couple).
- her determination and how she stood up for what she believed in.
- what she brought to the show overall(she seemed to be the only character that truly seemed real with a believable life).
- and everything else in-between.
It was torture to watch how the memory of Brenda was treated after she was gone. Storylines and characters were affected by her absence (sometimes rewritten, major blow to long-term viewers). You didn't realize how much Dylan and Brandon were affected until she was gone. They just weren't as upbeat as they were with her there. So there's another one: I missed who Dylan and Brandon were with Brenda present.