This is one of the lightest mountaineering boots and hiking boot hybrids we know of. They make just about any other boot feel heavy and clunky due to their light synthetic construction. They are the ultimate summer mountaineering boot as long as you don't need to do much front pointing and the temps stay at or above freezing during the day.
The main downside to the lightness is they don't take a normal ice climbing crampon (there is no toe bail). So you can't just throw on any pair of step-in crampons (you need crampons with straps or hybrid "semi-automatic crampons"). They are not ideal for heavy mountaineering use or ice climbing because they are not warm enough or sturdy enough. They are a little heavy and not breathable enough for warm summer hiking. They fit a middle niche for people that want a light boot to use in the snow or burly cold trail hiking, or alpine rock climbing (where you usually don't use crampons but occasionally might need them). Backpackers who carry monster 50-plus pound packs swear by them (you will never catch me backpacking with these or carrying a pack that big). They are ideal for hiking in the early season when hiking or backpacking when you might have to deal with both snow and regular trails.
Stories
I took these on a BASE jumping trip to Baffin Island as my only boot. Within minutes of landing, my toes began to freeze at camp. I quickly realized that for hanging out in sub-freezing temps, it is much better to use what the Inuit use, which are big and clumsy super-insulated boots. Luckily there was an “Inuit Wal-Greens” nearby that had a pair of big insulated boots on sale (believe it or not, even though it was 0 degrees out it was their "Summer Sale"). Once I had a pair of those, life was good again. In camp, I wore my arctic boots. When I hiked up to the top of the cliffs to BASE jump, I put on the Trango S Evo.
When moving, the Trango S Evo is plenty warm. Many of the other jumpers had burly double boots that made hiking in snow harder and putting on wingsuits hard as well. My Trangos were light, fast, and fit nicely in the wingsuit. On one approach to a jump, I decided to take a steep snow chute instead of the longer normal route. I was a little nervous, especially when the soft snow turned harder. But the Trango S kicked steps nicely and gave great sensitivity on the rock at the top of the snow chute. Most boots would have felt big and bulky when doing exposed easy fifth class moves, but these were perfect.
