I'm quite happy with my purchase. It took me a few hrs worth of searching through various options & decided to go with this one. My main reason was for a heat source for sleeping.To give background: My house is poorly insulated & don't use heat... it would be in vain due to the drafts of the house & be much too costly. I'm in the New England area of the USA & temps easily dip down to teens or lower (*F) during the dead of winter. In the house, I can see temps as low as high 20s F. The space heaters I do use on colder nights are to heat the plumbing in 2 areas.To rate the product: Some people were complaining of the rubber or chemical smell from the product. Yes, I do agree, there's a strong rubbery smell when 1st unpackaged. To aid in cutting down on the odor, I washed the water bottle, inside & out with dishsoap & the hottest water I could stand. This greatly improved that issue within minutes. I've had other water bottles in the past & there's always been some kind of rubbery smell, no matter the brand. So a slight odor (only when held up to the nose) was not that big of a deal.Another complaint I saw was the construction or the durability of the water bottle. So far, I think it's pretty well made. It's like a thick silicone material like that used with cookware items, except that this is glossier & seems easier to clean because of its glossiness.... as in filth wouldn't stick to it as much. Time will tell in regards to that.Up until now, I've used it overnight only a couple times to help keep me warm while sleeping. I've had no issue with leaks, and seems to stay warm for at least 4 to 5 hrs... hard to keep track while sleeping. I only used the hottest water that came out of my tap to fill it each time. I want to experiment & time the length of warmth it provides in the near future to give a better, updated review. I will test with both hottest tap & then again with slightly cooled boiled water from the stovetop.As of right now, I would recommend this water bottle. I have purchased 2 so far (one for my daughter). I also wanted to try this product under my coat while having to work oustide during polar vortex temps, see how bulky it is or if it's even worth it being used that way. Initially written 1-26-17***Update*** 3-23-17We've had such erratic weather in the NE Atlantic area, that I've had delays in using the bottle while timing & noting hot water duration. We had another arctic spurt yesterday, & used the bottle for heat while sleeping last night.Temps outside dipped to only the teens (°F), so my indoor temp didn't drop too low. At 11:00p when I started count, my room temp was 53°F (about 12°C). I filled 3/4 of the water bottle with the hottest tap water from sink, & 1/4 was microwaved (in a cup) to just shy of boiling. So the total amount used was 60ozs. & 15ozs of it was just shy of boiled. This warmth lasted to about 5am, with indoor temp down to 49°F (9°C), where it was still warmer than my body to the touch. Still, no leaks, with screwing cap just slightly more than finger tight but less than wrist tight (mechanics would know lol). I usually sleep on my side, but starting out, I slept on my back with the bottle mid torso warming my hands. Sometime during the night, I was on my side cradling bottle near tummy, almost as if it were a child there (as far as how much pressure on the bottle). This just gives you an idea of how much weight I'm putting on the bottle. Like I said, no leaks whatsoever. Hope this helps.I hope to update again on durability & using this for heat while wearing it outside for work, it just hasn't been cold enough here this year since this purchase.***UPDATE*** 6-19-17It's now basically summertime with the way the temps have been. Last night it was over 80*F and hard to fall asleep. This is the 3rd time I used the water bottle for helping me stay cool through the night, although last night I was able to time how long the the bottle stayed cool. I took it out of the freezer at 12am and it was still cool at 8:30am. Even though the it was completely thawed, it was still cooling me down. Still has condensation on it as I write this. (See latest photo.)How did I use this? I filled the water bottle 2/3 or slighter over and before I corked it, I compressed the bottle just enough so the air was just about all out. This allows for expansion whilst freezing, to hopefully make the bottle last or keep it from bursting. When I place it in the freezer, I also keep it flat on an incline so that the water line is just at the neck. I do this to keep the cork (screw top) from being damaged by the expanding water freezing.The only downside to using the bottle while sleeping for cooling is the condensation. This is not an issue for me so much, because it's not soaking my sheets and bed, they're just moist and easily aired out & dry within an hour or two from the heat.How do I use it? For cooling, I also sleep on top of it keeping it near my chest and tummy area. Whether I'm sleeping on my belly or side, this is my usual placement. This is an AWESOME bottle! I'm even more thrilled with this purchase and probably grab a 3rd to have a bottle to rotate with.