What is with the stretch side panels? I haven't seen this on any other parka. Seems like this would cost warmth with little upside.
No hood adjustment at all. WTF? Seems like this would be a huge PITA. Doesn't this make the hood next to useless?"
Yes the Atom LT is one of my main stay pieces for cold weather climbing. And one of my better investments in awhile for my own gear. I have and use two of them constantly. The vents are critical for using this jacket/sweater and do allow you to use a super light weight (as in .oz) insulated garment that is a lot warmer for the weight than anything else I can think of, because it breathes so well. Wild Things and Mtn Hardware have now copied the technology/design for their own versions. Hood is actually very good! No issue what so ever and easily fits over a helmet. It is extremely user friendly in fact.
The down sides? The shell material doesn't fair well rolling around on hard mixed. Rock climbing, chimney and off width, will shred them pretty easily. Soft shells are the weapon of choice there.
The stretch panels? They aren't very wind resistant. A lwt wind shirt under the Atom Lt will up the warmth in a cold wind. But the Atom is still no belay jacket imo. It is a climbing garment not a belay garment in cold weather. Think sweater, not jacket. The zipper? I had it pointed out to me that the zipper has no lock on it. Intentional by design to make it last longer I was told. I'd been using the Atom Lt for a year before I realised this fact. Read it actually. Loaned a buddy one of my spare Atom Lts and he hated the zipper. I have never, ever noticed it. So no down side for me at all. But worth knowing.
And the Atom LT can be used as a mid layer easy enough in the rock climbing situation to beef up the temps a soft shell can be used in with some comfort. The Atom LT's pattern and trim fit help there. It isn't the most intuitive way to layer (with a wind short or soft shell) but it works for certain projects.
Lightly insulated jackets (belay sweaters) and shells:
EB Downlight Hoodie Pullover XL 15.4 oz 455g
EB Frontpoint XL 18.5oz 547g
Arcteryx Atom lt Hoody large 14.4oz 429g
Arcteryx Atom Hoody SV 19.0 oz 562g
Mtn Hardware Compressor Hoody 19.8oz 586g
Arcteryx Gamma MX Hoody XL 24oz 710g
Arcteryx Squamish pullover XL 5.6oz 166g
On that list only the Compressor, Atom SV and EB Down Hoody are warmer. All are a tiny bit heavier and generally too warm to climb in alone as the 2nd layer because.....they don't breath nearly as well as the Atom LT. I will most typically add any of those three as a third layer when belaying or for climbing (more likely descending) when it is really cold out or the wind comes up.
It is a green Atom Lt in this picture with the black Compressor Hoody jacket used as my belay jacket over it. Pretty cold belaying in this picture and then again, I peeled the Compressor and just climbed in the Atom LT and a R1 hoody.
The Atom lt can be a mid layer for warmth. But I use it generally as a outer shell garment for cold weather climbing when I am very active. I no longer use a mid layer Some type of Hoody on the skin, likely a SAG Khushi, NWAlpine Hoody or R1. Then my 2nd layer, generally a Atom LT or a shell garment like the EB Frontpoint or a soft shell Arcteryx Gamma MX. The Atom LT (or anything similar in weight like the Nano Puff) is NOT a belay jacket...more a "belay sweater" and not that warm in the grand scheme of things if you are going to use it like that. Which I do if the temps permit it.
More here on what I think is a better layering system.
In the Ice fields late Nov. Good wind blowing while we discuss the avi conditions.
The Joke Slinger in his Atom LT at -20 something when the extra venting under the arms is crucial.
Another pretty cold day and in the shade. But that is the point, the Atom LT allows you to climb in relative comfort (and it was "relative comfort" on this day in lwt single boots) on some pretty cold days.
More here on the idea of a climbing sweater.