I've used Aspen's Spaceloft, Cryogel, and Pyrogel blankets and granular aerogel from Cabot in my lab and at home in MYOG projects, and it's my opinion that it will never outperform down or synthetic fiber insulation for jackets or sleeping bags.
As far as I know, all of the aerogel that has ever been used in outdoor gear to date (in POE pads, Burton jackets, insoles, gloves, etc.) has been aerogel "blanket", mostly "Spaceloft" made by Aspen Aerogels. I have a roll of this material at home and I sold some of it here on BPL a while ago. Under controlled laboratory conditions, aerogel blanket has a maximum R-value of R10/inch of thickness. The 9mm thick material weighs about 20 oz/square yard. So, an aerogel sleeping pad with an R-value of R10 would need to be constructed of a material that has a minimum areal density of about 55 oz/ square yard. Closed cell foams have a higher specific R-value (R value per unit weight) than aerogel blanket, and inflatable pads insulated with down or synthetic fibers are far higher.
POE has never been honest about the R-values of its pads. Roger Caffin collaborated with another author (whose name I can't remember) on a BPL article that reported measurements of the R-value of POE's aerogel pads. The measured R-values were less than 1/3 of the R-values claimed by POE (POE claimed R20, actual was R6).
Richard Nisley described some calculations in an old post (which I can't find now) in which he compared aerogel to down. He reported that high fill power, fully lofted down has about 50 times the R-value per unit weight of aerogel. An aerogel sleeping bag would be thinner than a down one of comparable warmth, but it would be completely non-compressible (like a sleeping bag made from closed cell foam), and it would weigh forty pounds. The same will be true of any aerogel jacket. Any cheap down jacket will be much warmer per unit weight than any aerogel insulated jacket.
Also, flexion of aerogel blankets separates the aerogel from the polyester fiber matrix. If you hold a piece of aerogel blanket with two hands and bend it fifty times, most of the aerogel falls out as clouds of dust. This is not a problem for pipeline or bulding insulation applications, which only subject the material to limited flexion during installation, but for apparel this is a problem. I examined the aerogel panels from a used Burton jacket a couple of years ago, and all of the aerogel had settled out of the blanket in a heap. The aerogel panel had become nothing but a layer of polyester felt with a pouch of aerogel dust at the bottom. The same will happen with the jacket discussed in this thread. It is an intrinsic property of the material. Many clever lamination/encapsulation methods have been used to limit the loss of aerogel dust from aerogel blanket materials, but even with encapsulation, flexion will cause aerogel dust to eventually settle to the bottom of the envelope, leaving only a polyester fiber mat at the top.Lamination/encapsulation does not inhibit the movement of aerogel particles within the polyester fiber mat. The aerogel particles will still eventually sink to the bottom.
Aerogel sounds fancy, and axioms like "it's the worlds lightest solid" are heard frequently, but compared to down, synthetic fiber insulation, and closed-cell foams, aerogel is very heavy. It's also not compressible, and any mechanical strain turns it to dust. Aerogel jacket prototypes were first announced in the media almost twenty years ago. If aerogel truly were what we all hoped it would be, the market would be flooded with aerogel apparel by now. Every few years, another company tries to use aerogel blankets as apparel insulation (Corpo Nove, Burton, Hanes/Champion, etc.), and they were all commercial failures because conventional apparel insulation performs better. The high-tech appeal of aerogel has not yet been able to motivate consumers to buy jackets that are stiff, heavy, expensive, and less warm than conventional down jackets.