Gotta read more carefully in the future. 4lbs did seem kind of heavy for a single chain saw blade of the "pocket" variety. Since I have a small axe in my "truck tools" kit, and a larger one at home, I never really considered it worthwhile to add one of these to my kit(s). If I was a trekker or woodsman, I might have to change my way of thinking.
In an urban surivival environment, it's use would be limited. Any "logs" small enough to cut with this device could be easily picked up and moved out of the way. It would also be difficult if not impossible to brace a 4 or 5" log enough to allow you to cut it with a pulling motion. With a real chain saw you are pushing towards the wood, which helps to keep it in place. You could probably cut down small "standing" trees, but I doubt I'd need a "lodge pole" in an urban/suburban environment.