[dtagames]

I would say generally, "Yes."

Definitely 80% of the bugs will come from 20% of the features. 80% of the usability and attraction is also from 20% of the features, but not necessarily the same ones.

Perhaps relatedly, about 70% of all software work is diagnosis and debugging. So a small subset of (maybe not so important) features causes most of the overall work in the project.