I looked for another thread on this topic but couldn't find one -- I was surprised!

I recently bought my first road bike (the 2011 Specialized Dolce, yum!) and am training for a century next month. It's probably going to be quite hot (Portland, OR), so I'm bracing for that and trying to figure out whether to buy insulated water bottles or not. Does anyone have any experience with them? The Polar ones get good reviews on REI.com .

I use a Klean Kanteen stainless steel bottle in my daily life and it fits marvelously into my bottle cage on my commuter, but on my new road bike it's a tight squeeze because the triangle of the frame is so small! I was thinking of getting a smaller sized pair of KK bottles with sport tops, but then I wondered if anyone else has other suggestions? REI now only sells BPA-free bottles and they have a great selection...but I do like the sturdiness of the stainless ones. It also seems like the opaque metal might keep the water slightly cooler than the translucent plastic ones... am I dreaming?

(The KK bottles come in a cute green enamel color that matches the green of my bike quite closely. ;)