Clayton, that's interesting about the Women's version using a thicker coating. I would like to trust their R&D department too but the company has a history of issues with quality control. Not sure if their R&D is weak or if there is some disconnect between the labs and the actual manufacturing plants. The latter would be my bet if they were manufactured in Asia but sadly this is a Made In America product (which opens up a whole 'nother set of discussion points about cost and quality of products based on location of manufacture that may temper some of the economist's rhetoric).
As for the technology, they use vapor deposition to aluminize materials. They basically "spray on" the aluminum. You're right though that materials and techniques could have improved but we're still dealing with a material that is very light, very thin and very flexible. This combined with attaching a metal to a plastic basically makes the entire manufacturing problem fairly difficult to improve. Most of the improvement from my understanding has been in speed, cost and consistency of aluminization (ie uniform and smaller thicknesses) not so much in strength of bond since until recently it hasn't been that much of a design constraint.
Personally I'm still not entirely sold that the aluminum even does that much. From what I've gathered they use more baffles in the Xlites than the original neoair (5 vs 3) and it seems to make more sense that the smaller baffles cause less convection and therefore provide more of the warmth gain in the new version. I'm not sure the aluminum alone can take credit for the ~20% performance gain. So for those worried, I think a worst case scenario is you'll lose maybe 10% warmth in laboratory conditions and probably less in real world since radiation losses are so minimal compared to conduction and convection. You are paying more though for the fancier materials. Of course though CD has been very good in supporting their products and that's rare in a company, design foibles aside,


