I think its primary function is to enhance head retention. 8oz of flaked wheat or 2-4 ozs of flaked barley would also work well.
If you just omit it, you'll probably notice no difference in flavor, but won't have as good head retention, I'm guessing.
Bottle conditioning: Robust Porter
Drinking: Saison Dupont clone, tripel
Coming soon: Columbus APA, Rich Red ale