Do you have any link to this product? I couldn't find it at Rei...
Hypothesing wildly, I would think such a vest has certain benefits and drawbacks. The chief drawback is that anything inflatable will be air tight, i.e. a vapor barrier. Moisture from your sweat will be trapped underneath. Trapping moisture will result in condense at some point. This may be a slight nuisance, no problem or a big challenge, depending on circumstances and what else you're wearing.
The benefit would be obvious: A (supposedly) very compact, lightweight and warm west. The only competing technology would be down, but quality down is ridiculous expensive and don't work at all when wet.
As for the benefits of a west - to really protect your core you need to cover your head area as well. Since the west doesn't do it your clothing must do it. A hooded version would be more demanding to make, harder to use without rupture, cost more money and be heavier - and would be MUCH warmer.
I'd like to see when someone makes a super compact and lightweight inflatable emergency shelter... something like AMK bivy bag, but insulated. These guys may or may not be close, I don't know anything about their product except their web site:
Blizzard survival bag