Definitely high quality material. Breathable, durable and super light. I always carry this one with me — for climbs in warmer climates, it’s always nice to have for early mornings/evenings. But for winter conditions, it’s my ‘extra jacket’, not the go to jacket for anything, really. It isn’t the one to keep you dry in rain or snow — not even for a bit (don’t think it has much resistant/repellent properties), so you need a real shell over it in those conditions. It’s super breathable — which also means you def feel the wind through it too...
bottom line, good for warmer conditions or as one of the parts of the layering system.

I'm a fairly active trail runner and mountain hiker (25+ mi/week avg). I've been attracted to Mountain equipment with their sensible and technical vision to mountain gear but I'm finding the size is too awkward for me and this jacket has limitations. Giving a review of this to hopefully better describe to people who are interested. I also have the Mountain Equipment Solar Eclipse Hooded Zip T-Shirt that has the same cut and fit.
This jacket is sold as a light soft shell and it is that however think of this jacket more like a thin wind shell. I own the Haglofs Alder hoody and I love, I cant say enough about how good it is and is always close to me, it's the best. I was looking for something to wear over my Alder (below 50 degrees) or just over a thin base layer/t-shirt .. I'll get to the size later, the material is interesting, it's very thin, don't think of getting much thermal properties from it and it has a crispy noise to it like a typical wind shell. The fabric appears to have a dwr coating on the outside. The jacket has good flexibility, I like the elastic cuffs. The weight of my XL jacket was 350 grams (12oz) on a accurate scale.
The size was awkward for me and limits my usage, I have a athletic cut, shoulders of my typical shirts is 19.5" wide (seam to seam), chest is 44" and waist 32". Haglofs in XL fits me perfectly, this does not. Mountain Equipment's cut in XL is more for a thin tall person with bigger waist. I would say this XL would work with 18.5" shoulders, 42 chest and 34" waist. The shoulders and chest were too small for me and the waist area flared out, it was slightly big in waist for me but not baggy. The length was way too long for me, the jacket in the rear drop almost below my butt, like a cycling jacket. It was several inches longer than my Haglof jackets. The arms were long too. So the cut wasn't for me but the jacket also was too loud for me on the trail like a wind shel, couldn't hear my foot steps with it onl. Not sure how water resistant it is over the long term but new it look pretty good for a very thin soft-shell.
I felt the jacket was a bit heavy for what I would use it for with all the zippers and cords. For me It had a narrow range in what I would use it for. It weighs the exact same as my Arcteyrx Goretex shell, packs the same size and weighs much more than my 110 gram Patagonia Houdini wind shell. I feel in a pinch my Houdini does the same thing as this jacket. Again, I have the Haglofs Alder that has the Pontetorto Tecnostretch fabric that actually works in a light drizzle (10 mins max), very soft, quiet and flexible.
I think an excellent possible alternative is the Arcteryx SQUAMISH HOODY,

Some people say the arms are really long, but in my case they aren't long enough. I have a relatively high ape-index (not atypical for rock climbers mind you) and I find them short. Compared with Montane Echo and Black Diamond BDV, they are by far the shortest. They also are on the narrow side, which can be a problem with a layer under.

The fact that the outer shell (not a layer) doesn't have closure tabs or tight wide closures that hug your wrist (like TNF Apex for example), is a big miss in my opinion. Not only it makes the feel less "sure", but also allows for excessive jacket arm travel.

Overall, I'd still recommend it, given how light it is, the quality of the materials and zippers used, but in my case it's simply too short in the arms, so back it goes.

This jacket is light weight and super breathable. The fabric wears well over time and doesn't pick like other softshells. It is fitted so if you're borderline, size up. On the flip side, the arms are cut slightly long and are stretchy for great range of movement. The coolest feature is how the waist has a special drawcord so that you don't dangle two loops at your waist where things can get snagged. I like how it has a real zipper that never gets jammed and not the smaller toothed styles that most jackets have in this category. Most lightweight jackets are made to be disposable. Not this one!

very simular the ECHO . here is a reviw on the squall

http://rockandice.com/gear-reviews/shell-jackets/mountain-equipment-squall-jacket/

I received this jacket as a gift, and overall I am mostly pleased with its performance. I really like the material it is made out of, it is very breathable and light. I've taken it climbing a few times and it does a good job of keeping the wind out and keeping me slightly warmer than just wearing a shirt.
However, the fit of it is pretty different compared to similar jackets from other brands. I am a solid medium across the board for jackets, but the echo fitted snug to my body and was a tad short for my liking. The tightest region was in the arms. There is a bit of stretch to the material, but when I bent my arms it would constrict around my elbows to the point of being uncomfortable. I have pretty normal sized arms and have never stumbled into this problem before, so this observation was new to me. I was surprised that a jacket aiming for climbers would be so tight in that area. This was the first Mountain Equipment product I've used, and I would definitely consider sizing up if you want complete range of motion, especially while climbing. If that is taken into consideration, it is a great piece to add to the quiver.