And... to add to my question as to which size you have and how you like it, do you have the loop top lid or the other (rounded dome)?
My other concern is that the bottle will sweat. I haven't found a solution to that, so I'd love to hear if you know of bottle holders (maybe neoprene, but those always get kind of stinky) or solutions to the sweating problem.
I love my Siggs. I have a few of them, smaller and the L size. Go with the Liter. I'd say it's the best size. ...mine doesn't sweat....At least I've never noticed it. I also have both types of tops. They're interchangeable.
I was thinking of the liter but not sure it would fit in car holder. Glad to hear yours doesn't sweat - I thought somene else said they didi sweat if you put ice in them. I could be thinking of something else.