Luigi at the Guerlain counter applied the Lingerie de Peau to half of my face to show me the difference between that and my naked skin. Its one of those foundations that are made to look like your skin but better. What sold me was not only how it looked (it looked like air or very airy, sounds kinda weird but thats the word that comes to mind), but the technology behind it. Its a lightweight sheer to medium coverage foundation that is designed to fuse with the skin, using synthetic and natural fibers that are undetectable.
Overall I think this is a good daytime foundation because of the coverage and the look that it achieves, but in terms of lasting power I'm not sure how long it actually lasts on my skin (but is that because I can't tell its still there since its supposed to look natural?) It does look great for the first few hours, but I find that I have to blot more during the day than my other foundations. I think I'm going to try it out when the weather gets colder to see if it improves, maybe its a better fall/winter foundation for me? Will update my opinion in a few weeks.