Definitely useable and helpful, but nothing special. Other than coming in unique sizes, this zip lock bag doesn't seem to be much different than an ordinary clear, plastic ziplock bag you can get in a grocery store. They don't seem to be particularly heavy-duty, so I assume it'll last just as long as an ordinary zip bag . . . in fact, maybe a freezer, zip lock bag from the grocery store would be a better quality.
I put all my stamps in plastic storage bags if there are several stamps in the set. I don't want to lose any. I have tried several ways to store all my stamps and this works best for me. I get two different size of bags. I even cut up magnetic sheets to fit in the bags and put in my dies for storage that way. If I have a matching stamp and die set, I use two bags and put them together with a rubber band.