If you travel in snowy environments, you've probably used or needed to use a bomber warm jacket. However, the downside of that is that you are going to need to carry a lot of weight. For travel in environments like the Cascades, where we get cold, but not quite as cold as a continental snowpack does, the Helios gives the right amount of warmth with not an ounce of extra weight added. I carry my Helios when I am doing winter overnights, and sometimes on summer/spring/fall overnights if I am going high enough in elevation. Oh I also bring it if I am cragging and just don't want to worry about being cold. "Michelin man" is my go-to style for that ;)
I wear my Helios when the temps go around 30-0 degrees F. It doesn't have a baffled box sewn construction, so there is a potential for me to feel a breeze if I am standing around on a gusty day, but I have never encountered that as a problem yet during my trips. The hood is very helmet compatible, but also cinches down for when I am not wearing a hood, and those clamshell pockets are just magic. I think it is a brilliant way to have a warm pocket that doesn't drop items. Weighing only 18oz, containing 900fp down, and packing down to the size of a nalgene, it is an easy choice when I am doing overnights.
The cut of the jacket is designed to be a "belay parka" style, and therefore is cut short so that you can have easy harness access. This is great for some, not so great for others. Just know, it's not gonna cover your butt. That said, I don't find that it rides up too much on me or comes up short.
Dan in his Helios climbing at Squamish
PROS:
Really warm for travel in the Cascades outside of high altitude winter activities (8-9k plus)
Sizing is pretty straightforward. It's a unisex jacket in a men's size run, so women just need to size one down from what they usually wear. I am a Medium in most women's clothes, and I wear a Small in the Helios.
For it's warmth it is really light
Shell material combats the snow and wind great. Don't wear it in a downpour though, as the fabric is not completely waterproof.
CONS:
The short cut can be un-ideal for people.
Some wish the bottom hem had cinch-ability, but it is just a lycra hem. I haven't found this to be an issue but it is something to consider.