Well personally, back in 2010-11, I wished I could have unchecked the spam and humor sections, for example (at first they were actually one big section), as well as the programming help sections, because when I wanted to check new projects it was annoying to scroll through dozens and dozens of topics I don't want to read and I couldn't provide much help of my own so I didn't bother much about help topics.
Nowadays it's not a big problem since Omni gets 50-100 posts a day most of the time, but when we get activity spikes like when the 84+CSE got leaked or when many topics are active at once it's harder to follow.
At least it's not as much of a big problem anymore now that the spam section is closed, though (and some of the more spammy users went mostly inactive shortly after it closed).