The Magni mid layer I've had for some time, it has gone on all levels of outings; full winter days, horrible wet days, rambling hill walks and even some day to day "lifestyle" use. Jöttnar have not set out to create lifestyle gear, it is not their focus, the Magni is comfortable so it's difficult not to reach for when heading out anywhere.
During a winter scramble up the Big Buachaille I pushed quite hard up the route in a baselayer and the Magni, the Polartec fabric fended off the wind. The sweat transfer was visible on the surface of the Power Stretch Pro material. Due to the wind the moisture evaporated away beautifully. This was my experience in the main with moisture.
Jöttnar describe the fit as athletic, I would agree completely. It fits well and due to the stretch of the fabric it is in no way restrictive.
Now, thumb loops, the thing with these is you either end up with the sleeves being too short that the loop cuts of circulation to the thumb or they are a bit too long whilst being worn and the sleeves have a bit of excess up the arm when the loops are not in use. The Magni sits in the latter category. They are not obtrusively long but there's some extra fabric to be managed, which isn't a chore.
Linked to the thumbloops but mainly an issue with the Power Stretch Pro, the material is quite thick. When moisture becomes excessive, like during heavy rain or when using the loops on wet surfaces (melting ice or scrambling on wet rock) the fabric holds a lot of water if it doesn't get the chance to wick slash evaporate. In fact one day when it was pouring rain I had it under a hardshell, the bum scoop sat lower than the hem of the hardshell and the Magni actually sucked up water making me wet to my mid torso. This was an isolated issue but one to consider on wet days.
The length of the mid-layer is one of the Magni's strengths, regardless of the soaking up occurrence. It's a good defence for the posterior with its long drop back. It goes under a harness and still has good use of the pockets on the front, and with the stretch of the jacket it didn't pull out, in my experience.
Jöttnar describe the hood as "ninja"! It is reasonably neat fitting, there are no drawcords to pull it in. The hood is tailored to fit under or over a climbing helmet. Without a helmet and walking into the wind the hood does balloon slightly, with nothing to cinch it around the head. I'm not suggesting it should have drawcords as it is comfortable under a helmet due to its cut. Again with the Power Stretch Pro's elasticity it will pull over a helmet and surprisingly (to me) sits really nicely. It's great for a wind defense when stopped on a ridge or at a belay stance.
The Magni's principal factors are the cut of the mid-layer and the Polartec Power Stretch Pro fabric. It is the coming together of two Goliath's. Jöttnar have orchestrated a great piece of kit that can be used in various mountain scenarios. The Magni is comfortable, stretches when required, lets sweat out and keeps you warm when the wind blows. It's a winter kit staple!