I've used this thermos all season with no problems. Like all thermos bottles, the key is to fill with scalding hot water 10 to 15 minutes prior to filling up with coffee, tea, etc.
I have used the NeoBottle on cold morning deer hunts and it works great. I needed a small bottle, small enough to fit in my pocket and it needed to be camouflage so it doesn't stick out like the bright white one I was using. This is the only one on the market I could find. It's perfect, small, camouflaged and keeps my coffee hot. I did not want one that would keep something hot for hours or that took an extra hand to carry.
Sound deadening the "tink, tink" of metal thermos was just what I wanted. But total inability to maintain a hot beverage, was not. Even with pre-heating, coffee was cold within two hours. Not lukewarm. COLD. Don't buy.