There are a lot of water bottles like this one out there for more money. I chanced this one, and I'm glad I did. I didn't get the 'sweater', because I don't like artificial fibers and I figured I could wrap it in something cotton for myself, so I can't rate that. But the water bottle itself is great.
Unlike the first bottle of this type that I got a few years ago, this bottle came out of the packaging without any noticeable scent and didn't need to off-gas before use. That was a nice feature.
I put an inch or two of hot tap-water (so, hot but nowhere near boiling) in it first, and then add ~4 cups of boiling or near-boiling water from my kettle. This results in a bag that is hot enough that I don't think it would be good for me to have it against my bare skin, though not hot enough to actually burn me just for handling it. I absolutely wouldn't make it that hot for a child, or for anyone planning on using the bottle without a covering against their skin, even tough skin on feet. However, what I do is use it to pre-heat a couple spots at the foot of my bed, and then when I get into bed, I wrap a thin towel around it and use it on my feet or legs. When it stays under my comforter with me all night, it's still noticeably warm 8-10 hours later.
I sometimes get lazy and leave it full at the side of my bed for several days before I need to use it again. I have never had it leak at all.
I am really happy with this purchase.