It's good to see that SIGG is a good solution for a lot of people here.
Sadly, I cannot say the same. I (and my wife) each had a SIGG for a couple of weeks, and it simply did not get along with us at ALL. It sweat all over the place when I put cold water in it, was difficult to carry with 1 finger, hung funny from a backpack when using a caribiner clip, had a narrow neck, so it was difficult to put ice in it or clean it (without purchasing a SIGG cleaning kit - again an added expense), and it was way too much effort to unscrew the top every single time I wanted a sip of water (yes, I know that there is the sport cap, but it is an added expense, and it is not nearly as practical as the Camelbak bitevalve solution). I feel the SIGG bottles are way overpriced, and just did not suit my needs well at all.
Then I discovered this GEM of a water bottle, and things have been peachy ever since:
CamelBak BPA-Free Better Water Bottle with Bite Valve
I went with the 0.75 liter in the charcoal color, and it pretty much solved all of the problems I had with the SIGG. I haven't noticed that the plastic has tainted the flavor of the water.
But for those who care, the SIGG bottles do at least offer a huge variety of colors and designs (if that is important to you), where the Camelbak bottles only come in a handful of colors, and no patterns or fancy graphic designs.