I got my bottle of YSL Le Teint Touche Eclat foundation in B40 when it came out last summer. This means that I've spent about six months now testing and comparing it to other light foundations I keep around. It's more than enough time to make up my mind about it, so I'll start with the bottom line:
As beautiful as the finish of YSL Le Teint Touche Eclat foundation, I will not repurchase it when I run out.
Now that it's winter, Le Teint stays put and maintains its finish for around 4 hours. Back in the summer the foundation faded much more quickly, taking with it any other makeup I applied over it. My skin is dry, so it's not a matter of hyper oiliness. Also, I've tried every primer I own or had a sample and none of them made any difference. So while YSL Le Teint Touche Eclat foundation is beautiful and looks naturally dewy, it's just not the right product for someone who expects their base makeup to last.
Now that we have that out of the way I can tell you that all the other YSL promises are pretty much spot on. The foundation gives a light coverage, evens out the skin, provides for a youthful appearance and has a subtle pleasant glow. I'm not sure what's with the odd number of SPF 19, but that's always a nice little bonus for those of us who like to pile on their sun protection. YSL Le Teint Touche Eclat foundation is east to apply with any tool from fingers to a damp sponge for building coverage (up to a point). The foundation needs to be buffed and blended into the skin, or it looks like a thick coat of a too dark paint (see swatches. I left it unblended so you can see the actual color, but take note of the texture difference between YSL Le Teint Touche Eclat and Chanel Vitalumiere that melts into the skin upon contact). It's a great base if you only need to wear foundation for a photo session or short event, but I need my face to last more than that. Do take note that the foundation is scented with something "fresh" (a citrus-cucumber?). The fragrance fades almost upon contact, but if you're sensitive this might be a concern.
Now for color matching. The very helpful SA at my local Bloomingdale's gave me samples of a few shades, even though we were both fairly certain that my match was BD50. I tried them in several light situation and it was, indeed, a good fit. I don't have a real match in MAC, and I've been described as anywhere between NC 25 to 35, so it's open to various interpretations. My undertones are fairly neutral with an unhealthy leaning towards ashy green, if that helps you any. As I'm looking at BD50 in gray winter light I do wonder if it's too dark or too peachy, so as you can see, even my own mileage can vary. The last swatch photo should give you a good idea why in real life I always mix and blend my foundation. Straight out of the bottle individual shades simply look off. Take into account, though, that none of the swatches were blended (and the amount of Guerlain Lingerie de Peau I accidentally used should have been enough for a full face, so it appears thicker and darker than it should be).
YSL Le Teint Touche Eclat Foundation ($55) is available at the counters, Sephora and on yslbeautyus.com.