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.