Durable but difficult to clean.
The bottle is sturdy (I dropped it so many times and yet it developed only a few tiny dents) and made of food safe (and BPA free) materials. It even kept my water fairly cool when working outdoors as long as I kept it out of direct sunlight. My only complaint is that it was not particularly clean-able. The water where I live leaves difficult deposits of various sorts behind (even when softened AND filtered) so reusable water bottles really need to be scrubbed inside, and it just wasn't possible to get it clean enough. If your household survives on bottled water, it's great, or if you have nice well or city water.
We have many types of water bottles in our house. The Sigg bottles are the first one we grab. They DO NOT leak!
I received a Sigg water bottle from my now husband as a Christmas gift one year and actually gave him the same thing in return (we had no idea we were getting each other the same thing). I love my bottle even though it's a little banged up because it reminds me to drink enough water every day. The taste of the water in the bottle is clean and refreshing and you don't have to worry about BPAs! There are a lot of color choices and the company itself is great!