I like tthem in a daypack when the water sources are good. I dip a gallon baggy in the water, stick in the straw and drink til its empty and then repeat. I first used one sheep hunting. We ran out of water and climbed over to a spring and drank our fill with the straws. Delicious. Unfortunately, they are pretty easy to plug and I don't know a good way to back flush them. I do pack some coffee filters and rubber band one on the end of the straw if the water is at all colored. Obviosly using them to fill containers doesn't work very well.
I like something like a Sawyer Mini or a Sawyer Squeeze if I am going to be refilling bottles or bladders.