I own (and have used) a Feathered Friends Winter Wren, basically the same thing as your Raku, including arm holes, but without the sleeves. (Come to think of it, I'm not sure mines baffled, either. Seems like a stupid thing to forget.) I have used it as my "mega camp parka," but I generally prefer to bring a spare parka. I just haven't found a good, convenient way of managing the "dress" doing anything other than lingering around camp. Depending on the trip, that might be okay. If you want to wander into the woods to gather firewood or something, though, not so fun. Basically, by the time I get the lower part hoisted up and kind of cinched around my waist it either hangs too low (I'm only 5'6") or is bunched up. I've pulled it up under my arms with reasonable success, though drafts up the bottom were a little annoying. I think there's just too much material there, especially when doubled over, to be fully functional for use. That said, if your other layers will mostly cover your active times, it is a great piece for the sedentary times. I personally wouldn't be comfortable using my only insulation both as a belay parka and sleeping bag--if I'm in parka mode, I'm generally not walking around in a snowstorm, ya know?
So for morning chores like the bathroom break, making breakfast, melting snow, even packing up gear--pretty great piece. When it comes to more active endeavors (I'm using the term leniently) like taking down a tent, I'd shuck the Raku and rely on your other layers. Most likely you'd be relatively warmed up at that point. I do wish my Rock Wren had the arms--nice touch!