My review of the green marble version applies to this product as well:
I saw a similar product at an outdoor cafe recently, and even on a hot summer day, it managed to keep a large bottle of sparkling water cold over a long dinner. Based on that, I decided to buy a set of these things and just keep them in the back of my freezer so they'd be ready when I needed one. Overall, I'm happy with the product - it's essentially not much more than a hollowed out block of marble - but it's easy to use and it definitely keeps bottled beverages at a cold temperature for a long time.
The size is slightly on the large side, perhaps half an inch wider in diameter than the bottles I normally use. I suppose it would fit a squat champagne bottle comfortably, but I suspect that the little half inch gap reduces cooling efficiency somewhat since it allows a layer of air between the bottle and the wall of the chiller.
It's also quite heavy, as you'd expect. An added benefit is that it would be pretty difficult to accidentally tip a bottle over while it's sitting in one of these babies.
One complaint is that in humid weather, the stone surface chills the surrounding air below the dew point, and thus it "sweats" fairly substantially. This isn't a product defect - just physics in action - but you can get quite a small puddle under the wine chiller that might damage (say) fine wood finishes if you're not careful.
My other complaint is that the one I received isn't black...it's more of a medium shade of gray. It works fine and all, just isn't as shown in the photograph.
Otherwise, it's a great product that does what it claims to do.