This reservoir has become an essential piece of gear for me on long and sunny backcountry skiing trips. I fill it to 1.5 - 2L for a full day and alternate between water and electrolyte-mixed water, and it keeps me from bonking. I was surprised by how sturdy and easy this thing is to use, and it's already withstood a beating going up Rainier, squished to the back of my backpack by camping and avalanche rescue gear.
The only thing I would like improved would be to have the volume measurement be more reliable, and maybe have a separate scale on the back? I'll fill it with some water, and it'll show 1.5L, but when I add another .5L of electrolyte-mixed water to the other pocket, it will still show 1.5L. To make sure that I'm bringing enough liquids—but not carrying extra weight—I've been using a measuring cup to pour into the reservoir.