Jeff from Oregon wrote a review of Marmot Zeus 1/2 Zip Jacket - Men's on February 7, 2012
I have three light weight jackets, the Montbell AlpineLite, Marmot Zeus half-zip, and a Patagonia Nanopuff pullover.
I wore each outside at several temperatures after sitting for about 30 minutes. I stood still for 10 minutes in each. I wore no gloves, hat, or shell, and Patagonia expedition weight top and bottom, and hiking boots as the only other insulation.
At 45f, all were adequate. The Nanopuff was only slightly warm, though it maintained the same warmth over time. The other two were both more than adequate. In a survival situation with this as your only insulation, any of these would have been acceptable, thought the Nano may not have been comfortable.
At 35f, the Nanopuff started out cool and became slightly cold after 10 minutes. Without a hat, gloves, and shell, 35f is beyond its sustained capability. IMO the Nanopuff is a good layering garment, but its ability to replace a normal jacket quickly becomes questionable.
With the 13.2oz Zeus at 35f, my hands and head were cold, but the jacket itself was adequately warm. Even without hat and gloves, one would survive at this temperature. Given a hat and gloves, the Zeus should be adequate if pressed to spend the night at freezing or slightly below. As the Zeus is only 3 ounces heavier than the Nanopuff, I see it as a far better general solution. It has DWR, a well-sealed neck closure and waist cinch, making it a far better solution in windy conditions as well.
At 35f, even though my head and hands were cold, the AlpineLite was very warm. Unlike the others though, the Montbell has both a hood and hand warmer pockets. With the hood and pockets in use, the AlpineLite is not at all challenged at 35f. I repeated this in the morning at 27f and again it was totally warm. While the AlpineLite is initially heavier at 15.7oz, for either of the others to approach its temperature ability, one needs to add a hat and gloves, if not a shell.