In natural daylight (note, I've packed it on for swatch purposes)
Under lamp light
Under fluorescent light
The Guerlain Météorites Compact Light-Revealing Powder is basically the pressed version of their original powder pearls. Guerlain did have an existing compact version called the Météorites Voyage, but it was prohibitively expensive at $191. It looks like the Météorites Compact is essentially an updated version of the Météorites Voyage at a lower price point. The new compact isn't as weighty or fancy (the silver is actually plastic), but judging from Temptalia's reviews, the product inside is more or less the same.
I tested the three available shades in the store and immediately dismissed Clair (02) as too white. The darkest shade, Dore (04), seemed entirely different to Clair and Medium (03), in that it had a distinct pinkish cast. I settled for Medium (03) as it seemed to be a safe bet. There's 10g of product which seems standard for a powder. When you open up the compact, there is a moderately strong sweet floral fragrance, but it doesn't linger when the powder is applied to the skin.
My main gripe about powders is that the surface ALWAYS seals. This happens to almost every single powder I own, blush and bronzer included. You can see in the pictures it's already started to occur. I'm guessing this happens because when I use the powder over foundation that's not completely set (and really, when does a foundation completely set so that subsequent contact with the skin results in zero transfer), I dampen the surface of the compact as I dip my brush into it. Those areas then harden, which 'seals' the powder and makes it difficult to pick up product later on. It also destroys the aesthetic of the mosaic pattern (which let's face it, was a primary motivation to purchase), given patches of brown are polluting the surface. At the moment, the problem's not so bad that I'm unable to pick up sufficient product with my brush, but it is an issue that I find nearly impossible to avoid entirely.
Onto the powder itself. This is a finishing powder, so it's not designed to set your foundation. It can be used after a separate setting powder, directly after foundation, or on bare skin. I prefer to use it over foundation all over the face, occasionally after a dusting of Chanel Les Beiges Healthy Glow Sheer Powder. The luminescence the Météorites Compact provides is a kind of ethereal pearly white. Under certain lighting conditions, scrutinising my face up close, it's straight up glittery. By "glittery", I mean I can clearly detect tiny white sparkles and ultra-fine shimmer on a translucent base. This is most noticeable under bright department store lights. The sparkles appear mainly white, but once again, depending on the light, they can also appear gold or peachy. On the skin however, the illumination remains white in character. Staying power is very good considering I can still detect the powder on my skin at the end of the day, though whether it's still providing any radiance at that point is questionable.
I'm still in the process of experimenting with the best brushes to use this with, and so far the Ecotools by Alicia Silverstone Finishing Brush is winning. It's basically a super soft stippling brush that diffuses and blends product to an airbrushed finish. I tried the Charlotte Tilbury Powder & Sculpt but found it on the small and stiff side, applying the product in too concentrated a manner. The Real Techniques Blush Brush was on the opposite end of the spectrum — a bit too large and floppy. My SUQQU Cheek Brush fared well, but it seemed such a waste to limit my use of it to a single finishing powder. I prefer to use it for blushes and highlighter, but I can't have remnant blush pigments in the brush tainting the surface of the Météorites Compact or subtly changing the nature of the powder. Beauty obsessive problems.
Overall, I suspect the Météorites Compact is comparable in purpose and effect to other luminosity-adding powders I've been eyeing: NARS Light Reflecting Pressed Setting Powder and Hourglass Ambient Lighting Powder in Diffused Light. Both are less expensive (the NARS is quite a bit cheaper at $46, while the Hourglass is $59), though the Guerlain wins in the packaging stakes. I'm slightly on the fence about the white tint and the shimmer/sparkle factor (though it could just be my heavy-handedness), but the effect from a distance is noticeably illuminating and diffuses the appearance of imperfections.