I too have used these (actually USED) it. Admittedly these are clearly not the best fire extinguishers in the world...but all else being equal you still have a better chance putting out a (small) fire with these than with nothing. Sure you can go guy a mega buck commercial (that needs serviced regularly) Halon or CO2 or other K extinguisher (I happen to also own multiples of each of those as well as a foaming system in our aviation business), but the reality is most people don't and won't bother to buy one of these, much less one of those.
My recommendation is to not count on this as sole miracle for all fires. In fact, some of the small "canned aerosol pressurized foaming fire extinguishers" are in some ways probably just as good or better....but, I'll repeat: Having one of these is better than having nothing and for the price you can't make much of an argument the other way. Given the price and availability of the A/K/other commercial alternatives just means most people can't/won't buy them (right or wrong). Again, I will concur these aren't super high end perfect extinguishers, but I would say they are better than doing or buying nothing.