I shifted to a bladder when I was ridge hiking in Hawaii. It was more convenient than bottles. I also like that I don't have to stop to drink, or take my eyes off of the trail or my surroundings - I can drink and move, and not have to take off my pack to fish out a water bottle. I used to use a canteen (strap and all) for this, but it didn't work well with my external frame pack when I started backpacking.