My Frost Line Parka showed up from Backcountry.com, so I can add a few initial impressions.
Fit
I'm a hair under 6'0 and 165 lbs. I ordered a medium after vacillating between medium or large. I'm really happy with the fit. Montbell stuff is usually pretty short in the torso and semi-short in the sleeves, so if you're a slimmer person you end up needing to size up to an oversized torso to get tolerable torso and sleeve lengths. The Frost Line is a much different cut, as Montbell claims.
The sleeves are nice and long. They naturally rest at 1/2 way down my fingers, which is what I want for a parka. The torso is way long for a Montbell garment but only normal or slightly short of normal in the parka world. The rear length is good, it's the typical mid-butt length you'd expect for a parka. The front rises higher so it's maybe an inch short of ideal but far better than most other Montbell products. My Montbell Alpine Light Parka was much shorter front and rear (and in the sleeves) despite being a size large.
The torso girth a good fit. It's a little big if I've just got a t-shirt under, so it fits nicely over a fleece or lightweight down jacket. If I was in the market for a urban-hipster down jacket I'd probably go size small to get a slimmer torso while still having decent sleeve and torso length.
Weight
My medium weighs in at 575g (20.2oz) which is 0.5oz over spec. Hopefully that's from extra down.
Critiques
The zipper snags easily on the draft flap. The draft flap isn't a down filled tube, but rather a few layers of soft fabric with seemingly a bit of down trapped in there. The fabric is the same light nylon as the rest of the jacket, so it's not stiff. Montbell should add a stiffener and/or position the flap so it attaches back a bit further from the zipper. The way it's positioned, it's begging to be snagged.
Comments
It's a bit warmer than I expected. It's a big step up in warmth over my Montbell Alpine Light Parka. It's should be ideal for most winter use and then I'll layer another warm piece under when it's really cold. For stupid cold weather you'd want something else. Overall I'm quite pleased with it, mostly because it fits well which Montbell has traditionally struggled with.
The hood is large, but cinches down well with good coverage. It seems like it'll stay in place well on windy summits. I personally prefer not to have a helmet compatible hood, but as far as helmet compatible hoods go, this one is good.
I'll likely take the sewing machine and scissors to this jacket sooner rather than later. I've never been a big advocate for zipper draft flaps, particularly poorly executed ones. Even with a good flap I find the function barely warrants the weight. Since this one snags, I'll probably nix it assuming I can find a way to do so elegantly. I'm also leaning towards removing some internal features. I almost never use internal stash pockets, and I will never use the smaller zippers pockets attached to these. If memory serves, the stash pockets aren't integrated with the external hand pockets, so the inner pockets can be removed without losing the outer ones. I might shave an ounce. Not a big difference but I like a simple jacket. I'll also probably color the white Montbell sitched on logo with a sharpie so it's not an eye sore on the dark navy.
Suggestions
Mostly this comes down to just making a good jacket lighter, but functionally Montbell should make the front an inch longer and fix the zipper draft flap.
In terms of weight, Montbell trimmed a lot of fat off the Frost Line (4-6oz?) for the 2014/15 version, but they could go a little further. I'd like to see at least the internal zipper pockets nixed. I'd also like to see the use of lighter fabric internally. 30D outside and 10D inside would be great. Switching to higher FP down would be sweet, but that would raise the price and make it too similar to the Mirage. More practically, Montbell should switch to smaller cordlocks. The waist cordlocks in particular are overly beefy considering they'll likely be adjusted initially and then very infrequently after that.