Well, I've had a quick go on some bits of wood out of the scrap box. I was disappointed at first. I had tried sharpening just on the inside of the wings. This was difficult, there's only just enough room to get a needle file in at the right angle. Results were ok but not great.
Looking again at the bits I already have, I found that I did have two of this style already. They worked much better. They had been sharpened on the outside as well, so I did the same on the two I bought today, being careful to leave clearance behind the cutting edges, not a bump. (This has the advantage of only needing a small flat file, which most workers would have already had for other, commoner augers.) Success.
Once they were sharp, the bits all cut well, in side grain and in end grain, hardwood and softwood.
I'd say they are especially useful if you need a hole at an angle, as the rounded edges work better than the scoring cutters on a scotch auger when meeting an oblique surface.
And they are perfect if you need to deep countersink a screw, you can bore out for the screw head then use a smaller bit in the middle, where the leadscrew was, for a clearance hole.
All of this applies to the solid nose style too, but the Cook/Gedge/Gilpin design is a bit less liable to clog.