Well, as Pizzaman pointed out, they mostly seem to be backwards. That being said, I prefeer either a partially serrated blade, or a serrated blade with a straight edge in one knife. I think they are worth while one heavy, fiberous material, like webbing, rope or cardboard boxes. Curogated carboard is hard on edges, and I would say it takes about half the energy to cut them up with a serrated edge than with a plain blade. With some informal tests, I would say that serrated blades don't cut rope or webbing as cleanly, but much more quickly.

And they go through leather a lot better. If you are on or around reclaimed pasture land, you know what kind of weird stuff lies lurking in the underbrush a hundred years later. I've never had to cut my boot off to get unstuck, but it's been close a time or two.