I've never used this product, although we have discussed it in the past. The principle behind the product is sound, and it does have some advantages over some other products, such as not producing heat, but the one huge drawback at the moment is that it only comes in "band aid" sizes for consumer sales.

My wife did once slice off a good chunk off the tip of her finger with a very sharp kitchen knife, which bled rather profusely, and this would have come in handy but besides an injury like that, I'm not sure how useful the "blood stopping" capabilities will be for general use since our bodies stop bleeding from run-of-the-mill cuts and scrapes pretty readily (that is, cuts small enough to be covered with these bandages). If you're dealing with people on anti-coagulants, like an elderly parent, then I can see some benefit, but that's pretty much it.

That said, I don't see any reason not to have these in your kit, if they seem interesting to you.