I've used a "backpack" for at least 5 years now.
for the last 3 years I've been using a Wing Nut Gear "enduro" http://www.wingnutgear.com/product_d...product_id=151

I have a tendency to mix the likes of Perpetuem in a bottle and clean water in the hydration pack.
also I use the hydration pack for in camp duties.