I spent a good 5 months searching for and trying on different winter boots. I found that for peak ascents and more serious hiking and backpacking in the northeast, that a double plastic was way overkill, yet a boot with support and proper stiffness is important. Most insulated boots cause feet to sweat way too much. The danger is then that the boots may freeze overnight, or just be uncomfortable during the day. Nothing worse than sweating through your boots, even if they are "breathable." After much research and ordering and returning of different boots, this was the absolute best choice. These boots are really well made, and are definitely waterproof (had them covered in snow for hours, the outer layer eventually got wet, but no moisture made it through to my feet.) They are also the most breathable winter boots I've ever used. They are rather sturdy, allow just enough flex for comfortable winter hiking, and take crampons and snowshoes quite well. They are also a good deal lighter than many similar boots I tried, and you notice it on the trail. Nothing like really feeling your footing rather than feeling like you are walking on a plastic platform. I went up a whole size, and use them with mountaineering socks and wool liners. My feet were almost too warm when the temps approached 30. In the 20's my feet were warm the whole time. These boots have enough room in the toe box for me, and are cut on the same footbed as the salewa mtn trainer gtx, so you can go to your local ems and try them on to see how they fit before ordering these. The last point is that these boots have an amazing little feature - a two layer footbed which can have one layer removed. This is awesome both because it allows for more volume if you are in-between sizes, but also allows for adjusting your level of sockage based on the weather. Want one thick pair? Leave in both parts of the footbed. Want layered socks? Take one piece out. Definitely recommended for winter use on the trail. Also recommend for general mountaineering on lower peaks and where a double boot is overkill. There is a great little approach section on the shoe, and without the crampons these make great scrambling shoes, and will do really well on exposed rock. I'd say they are too heavy for summer use, but if you really wanted to make it happen I think it would be fine.