I've been testing one of these for a while now. Your mileage may vary; I've no idea how representative my sample might be, but I've been pleased with it.
For starters, it is, well, an umbrella. The umbrella part works fine. I couldn't find sufficiently stormy weather on command to pull it inside out to see what would happen, but I tried whipping it through the air as hard as I could while it was open and did not manage to damage it that way.
I've flexed it but haven't yet broken it. I've beaten things with it, though I've tried to preserve the umbrella part so I can use it as, you know, an umbrella. (It's the CORE of the umbrella that is supposed to be unbreakable, not the relatively fragile umbrella parts. At least, that seems the only realistic approach to this that I can see.)
I gave it to a New York City Bellhop as part of a load of luggage and he managed to smack it into every wall he could find. I scraped the wall paint and plaster off the handle and there was no appreciable damage (just some scuffing to the handle itself).
Barring any extreme Cliff Stamp torture testing, I'd say the umbrella performs as advertised, though I must advise that I have not yet fought any ninja with it, nor any pirates, and the asking price may be steep for some. It's really a pretty class umbrella that is also a functional self-defense tool, and I'm happy to have mine.
6 months a year, you either have an umbrella or some nice Goretex outerwear.