I've had this product for about 3 weeks. This is a nice canteen, keeps liquid cold as advertised. I have a couple design suggestions.
The lip is a hard metal edge, with an exterior plastic ring around it- the plastic ring is part of the latch. When drinking from the bottle, it feels strange on your mouth. The metal is thin and sort of abrupt- no beveling, and the top of each component is uneven by about a half millimeter. As a result of this difference, your lower lip does not sit flush against the surface when you drink from it. So drops of liquid catch on the lip of the bottle, run down between the metal and plastic, then run down the exterior. (Maybe this slight gap is a flaw with just my bottle.)
Because this is a growler it's expected that the liquid will be beer, and the beer ends up making the exterior of the bottle sticky, and you end up with sticky hands and a sticky backpack. Of course it's advertised as a growler not a canteen because its intended use is to pour into cups, not be sipped from. But this is an item designed for travel purposes, hypothetically outdoorsy stuff, and one can't be expected to bring both this container for beer plus drinking cups anytime they use it. A mouth on this bottle with a beveled edge that you can functionally sip from would be would be better.
The second thing is that there should be a ring or extrusion of some sort that makes it easy to hold and carry. I know the larger growler has a handle, but it's a little too big to comfortably toss in a backpack. When I bring this thing to the park I need to bring a bag just to carry it. The diameter is slightly larger than what would be a comfortable grip, the exterior has matte paint which stays slick, and when it's full of liquid it feels like it could easily slip from your hand. And I have hands on the larger side.
Lastly, the uneven top is a small negative feature. If it were level you could place something on top of it when closed, like your cell phone, or cutlery, or small objects you don't want to put on the ground or lose when camping. Not that that is something that happens all the time- but making the top slightly uneven means the designers have sacrificed functionality for appearance.
That aside, it looks nice, it insulates well, and the latch and seal are quality.