David B.wrote a review of La Sportiva Karakorum Mountaineering Boot - Men's on March 7, 2013
Familiarity: I've used it once or twice and have initial impressions
Bought these boots for a spring backpacking trip in the Sierras. I got to use them for the first time a few days ago on a winter hike up Mt. Chocorua. They kept my feet toasty warm (it was mid 20's and I ended up wishing I had lighter socks because my feet were over-heating a little bit). I hiked 7.5 miles right out of the box with no blisters and not a single hot-spot.Not bad for such a stiff shoe. They worked well with the BD Contact Crampon Clip (I wear a 45.5 and they were right at the upper range of the crampon).
I water-proffed the leather with Nikwax before use. With temps below freezing I would have been worried if I had issues with waterproofness. I will have to report back when I use them in warmer conditions.
My only complaint is fit and this is really specific to my foot. They are low-volume boots. I have what I would consider a normal or medium width foot. I ended up having to go up about half a size from what is my true shoe size. As I said above I remained blister free. I did, however, find that when I went on to the front point my heel raised quite a bit. I had not experienced this when I walked on an incline slope without crampons so it came as a bit of a surprise. Not terrible for me since my primary use is backpacking and hiking, but worth keeping in mind if you have wider feet.