They aren't flying off the shelves, but early signs are that Snow Leopard boxes are far exceeding sales of Leopard, and 4 times higher than sales of Tiger.
That's the assessment of the NPD group, which tracks retail sales for many industries. The firm also notes that sales declined about 25% from week 1 to week 2, again, far better than both Leopard and Tiger. Tiger was released in April of 2005 and Leopard hit the streets in October of 2007.
Of course, Snow Leopard sells for US$100.00 lower than the price of previous versions of Mac OS X, so that could be a large part of the success of the release.
Stephen Baker of NPD noted, "As we head into the fall selling season, and the release of another major OS upgrade, it will be instructive to see if that upgrade (Windows 7) -- currently projected to sell at ASPs much higher than Snow Leopard -- can deliver the same incremental increase in consumer demand that Snow Leopard has enjoyed."
As we've noted, the update to Snow Leopard has been a bit bumpy for some, but by most measures of satisfaction and sales Snow Leopard is not at all like the mammal it has been named after -- which is, sadly, endangered and diminishing in numbers.