I’m really impressed with this jacket and the lighter-weight version (transalp something). Polartec Alpha is a really nice insulation. Just warm enough to keep you comfortable while moving (this is not a belay jacket), but somehow without overheating. I was perfectly comfortable in windy 30’s in the transalp today with only a long sleeve t-shirt underneath. I’m 6ft and 160lbs, I have a large in the Mezzalama and a medium in the transalp. Both fit well, but I do prefer the sleeve length in the large. It is a great layer. I haven’t used them in really brutal conditions yet, but can’t wait to take them out.
In the new world of air permeable insulation layers, the Dynafit Mezzalama 2 Jkt holds its own. The reason you might want one of these new-fangled layers is that they work well for high exertion activities in the extreme cold. Most likely backcountry skiers, tourers or casual racers would only use this in transitions or in extreme conditions, the weights of these dual purpose jackets is just slightly heavier than down or synthetic insulation.