I've used an inexpensive wharncliff to cut roofing paper, so the tips aren't that weak. Very good blade for rope/hose or any kind of "sawing motion" sort of cutting where you don't have to change the angle of your wrist while you cut. Also very good for cutting on a surface, like slicing tape, soft wood, thin tile, or cardboard that is already laying on some other surface, the kind of cutting you might otherwise do with a razor blade, boxcutter, or x-acto knife. OK for vegetables and things like that, but not for dicing or meat cutting which requires some belly.
I'm not a knife fighter by any means, but I can't imagine the shape would be too good as a defensive blade. If you thrust, the tip will penetrate, but only the lower edge will cut, the rest will only push tissue out of the way. If you slash, the tip will engage the target, but there will not be as much edge applied to the cut as there would be if the blade had a belly.