I disagree. From the article: "The same year Apple launched the iPhone, it unveiled a massive upgrade to Mac OS X known as Leopard, sporting “300 New Features.” Two years later, it did something almost unheard of: it released Snow Leopard, an upgrade all about how little it added and how much it took away. Apple needs to make it snow again. Snow Leopard did what it was made to do. It was one of the most solid software releases Apple ever put out." This gives the impression that it was solid out of the gate, which it was not. And the next paragraph specifically mentions "2009’s Snow Leopard". But later Snow Leopard releases were in 2011.
Grandempire is right on my overall sense in the piece, though perhaps I should have made its ore explicit. I actually faired quite well with 10.6.0. But, the lack of push for a yearly set of headlining features did allow the OS to age quite well in the years after, too. It's the drumbeat of what 10 stunning new features will be unveiled each WWDC for each platform that means past features rarely get the continued polishing they need to shine.