I bought these boots about two years ago on Amazon.  I was looking for a boot that would take me warmly through the Indiana winters while affording me the same warmth when climbing mountains in the spring.  I am happy to say that these lived up to my expectations. Since their purchase, these boots have been to the summit of multiple peaks and buried under feet of snow.  My feet stayed warm through it all.

There is one caveat to my review that made this a 4 star as opposed to 5 star worthy boot.  The toe box will get cold if you are sedentary for too long in cold environments. They are fantastic when you are moving and to an extent, this is a good thing if you are an active hiker.  Keen claims there is more insulation in the toe box, which may be true.  I believe, however, that with a little use, the insulation in the toe box becomes abused and compressed which lessens it's effectiveness.  That being said, I wear these boots with SmartWool Mountaineering Socks and they provide extra insulation that makes up for the compressed toe box.

If you want to stay warm without compromising technical ability on the trail, buy these boots.  The new model is no where near as good as this one and is geared more towards shoveling snow in the driveway than blazing an icy trail in winter.