I've had a number of stainless steel water bottles, including the Klean Kanteen (which was great until a cafeteria worker threw it out, yes threw it away, when I left it in the cafeteria). I've had my Shinzi Katoh 500 mL trekking bottle now for over 6 months and it is by far my favorite bottle yet. It is double insulated so it keeps water (or whatever) cold for hours without getting condensation all over the inside of your purse. I haven't tested it on hot drinks yet, but I will soon. The opening at the top is the perfect size. The only thing you need to watch is making sure you clean the rubber ring on the lid frequently.
Like all Shinzi Katoh products they are super cute too. I have the "In The Ground" 500 mL bottle and I love the colors and woodland creatures. We keep it on our night stand and I love rolling over to find cool, fresh water in the middle of the night. I'm looking to get the "Many Apples" 300 mL bottle next for my handbag.
You can find Shinzi Katoh trekking bottles here, here and here. You can also check out the official website here. They also carry adorable bento boxes, tea sets, trays and linens.