I only need about 2 inches of plain edge. So if a knife has a 4 inch blade, I do not mind if 30-50% of it is serrated. Sometimes I prefer it.
It seems most people here dislike combo edges, but I have found them to be VERY useful. Plain edges do some things better. Serrated edges do some things better. I understand the whole "combo edges do not give you enough of either do do any good" arguement, but I feel it only applies to smaller knives. With larger blades, a combo edge gives you enough of both and makes the knife very versatile.
With each knife I buy, whether I decide to get the plain edge, combo edge, or serrated edge (assume I have all three options) just depends on the specific knife, what I want to do with it, my mood at the moment, and the visuals of the knife. Some knives look great with a combo edge. Some look horrible.
Two real life examples:
When cutting plastic stretch wrap, a plain edge is better than a serrated edge. You can just lightly slice though it, while a serrated edge can hang up. When using a combo edge to cut open wrapped pallets, having around 30% of your edge serrated can reduce the effective blade length. Annoying.
When cutting hard plastic strap on pallets, using a plain edge can be tough. A serrated edge, however, makes very short work of the hard straps. As in, you simply touch the strap with the serrated edge and it just breaks open with no effort. Like a light saber. No plain edge, no matter how sharp, makes such short work of these straps, and no more than a fraction of an inch of serrations are needed. So when I have to cut these straps, I am very glad to have some of my edge dedicated to serrations.
Why not use a fully serrated knife? Because it is a waste in this case. I do not need 3 inches of serrations. I barely need one. And when I have to turn around and cut open a wrapped pallet, I am glad to have at least *some* plain edge.
YMMV.
