I often mix canned pumpkin into my dog's food, but as others have pointed out, it can sometimes go bad before you finish the can (I freeze mine in ice cube trays, but then you have to think ahead and make sure it's thawed and ready to use when you need it). My dog tends to be pretty picky; I've seen him pick a blueberry out of his bowl and set it aside with the precision of a brain surgeon. So I am always cautious when offering something new.
Sprinkling it on his food did not go over well, there was something in the taste or smell that didn't get past his fussy nose. So I ended up putting it on the bottom of the bowl and stirring well. That did the trick. The texture is like a fine powder, so it's not hard to camouflage in his food; I've even made it work for my cats.
It does seem to help him with his digestion; he doesn't have a lot of issues in that regard, but sometimes the stool is harder than usual. Adding this to his food daily seems to help maintain a normal stool pattern, so it is effective, as claimed, at firming stool.
The ingredients seem all-natural, which is a huge plus, and the instructions for both dog and cat are clear and easy to follow. Since you don't use much, the container should last a while, making it a great value. However, one cannot deny that a simple can of pumpkin --while missing some of the other ingredients--is much less expensive.