I don't use them locally because I never ride further than my two bottles will last without passing by a store. I have found them invaluable when I go to Colorado each summer. Both on the road and the trail. One advantage to me is that I can carry a packable rain jacket. Temps can go from the mid 70-'s down into the 50's in a rain storm. Soaking wet 50's is miserable. I also throw a camera (yes a real camera) in my pack so that I can take good quality pics along the way.

People keep mentioning mold. I have average size hands and I can reach into my bladder to dry it out.