One thing to add:

Before I bought my motherlode camelback, I had a big day pack with several 300 ml and 500 ml bottles of water packed inside. It was convenient as a bob, except for when I was needing a drink of water and had to rummage the pack after doffing it.

Also of note, water stored in a camelback bladder over time is still more pallatable than water stored in plastic bottles. If you open a bottle, what you don't drink won't stay fresh very long. In Iraq, we were ordered to dump any unconsumed water from opened bottles rather than stow the container for later consumption. If the water was poured into a camelback bladder (properly maintained), we were allowed to keep it in there indefinitely. Things that would grow in previously opened water bottles would not grow in a cb bladder. Anyone here know why?