well, really. what more could you want with a water bottle. It holds enough, clips to your harness, doesn't leak, doesn't crack and it's light weight.
Mine is covered in dents, chips and scratches and still looks good and provides it's primary function of holding water without leaking. Pretty straight forward.
I even filled mine up and froze it. Didn't crack with the increased pressure, instead the bottom of the bottle just bowed out of shape to accomodate the increase in internal volume. Reassuring if freezing is a risk (ie: alpine climbing).

I wonder where the previous reviewer got his/her information about the breakdown of the Sigg liner. This is on sigg's website: http://www.mysigg.com/index.asp?PageAction=Custom&ID=5

I know you're thinking of course they're going to say that about their own product. But I'm wondering where ilovealiens gets their info.

Aside from the obvious problem of having a water bottle that looks identical to your fuel bottle, I assume you tried sigg due to the Nalgene recall?? However, it seems that people have forgotten about the toxicity of plastic bottles.
"Bisphenol A is added to hard, clear polycarbonate plastics like those used in reusable water bottles and baby bottles....Research on lab animals has linked the chemical to changes to the genital tract, prostate enlargement, declined testosterone levels, pre-cancerous breast cells, prostate cancer, early puberty in females and hyperactivity." Aluminum bottles pose severe health risks, and there is a proven link between aluminum intake and alzheimers disease. The veg based liner in the Sigg bottles wears away and chips when dented exposing you to the aluminum.
The best option is a stainless steel bottle, such as "Guyot
bottles" or "kleen Kanteens"
Using an actual fuel bottle poses other risks as the lining is made not for drinking out of, but rather to prevent the fuel from damaging the inside of the bottle.
yuck.

I love these bottles. They can take the abuse any climber can give them. I've taken mine out, and they are pretty badly dented, but that just gives character, right?
For someone looking for a new bottle, these are the way to go. With all the talk about Bisphenol A, I just enjoy the peace of mind that goes with an aluminum water bottle. I've never had any problems with the lining cracking and leaking to the drink, and I've had it for 2 years.
Bottom line: Fashionable and durable.

Yes I know you are talking about SIGG bottles here but I must tell you about a primus bottle that I
bought of the same design. It got one little dint in it and the inside coating came of by the dinted area. I found this when I got the coating in my mouth. Me thinks SIGG might have the same problem.
I will just stick with my Nalgene bottle until some one can convince me otherwise.
Happy trails.