Are you a troll or are you serious? MacOS9 to OSX isn't a service pack difference. It's like going from Windows 3.1 to NT. And saying that OSX is solid doesn't mean that earlier versions of the Mac OS weren't good any more than saying Windows XP is solid is saying that Microsoft OSes starting with DOS were worthless. But keep comparing apples and oranges if that's what you've gotta do...
Ok, let's say OS X 10.0 vs. 10.1.