I bought one of the leak proof backpack bottles at the beginning of this winter (Thanks TsPoet!) and I love, love, love it. It keeps hot stuff hot for hours, even when its miserable 39degrees and raining here. I bought a piece of neoprene and sewed a little sleeve for mine to keep it from rattling around too much (I used an old sock before I bought the neoprene). I got a little razzing from my teammates at first, but hey, when we were all standing around freezing, waiting for someone to change a flat and I could pull out my nice hot tea - who's laughing now

I did find that I did not want to pull it out while riding to drink - because it keeps things *too hot* to not risk burns.... I suppose I could temper that by not filling it with boiling hot drink in the first place, but then it might not stay warm as long (I've had stuff in there that has still been warm the next morning though!)