Let's start out with the most basic reason Windows 8 isn't as bad as Vista: Windows 8 will likely gain a greater market share than Vista ever did. According to Net Applications figures, Vista's greatest market share for a year was only 17.73%, in 2009. Windows 7 very quickly eclipsed Vista after it was released.
All this doesn't mean that I've suddenly become a fan of Windows 8. I still think it was a mistake to build a single operating system for tablets and traditional computers. And saying that it's better than Vista isn't much more than damning it with faint praise. Ultimately I expect that the next major version of Windows may well fix many of Windows 8's problems, the same way that Windows 7 did for Vista.
Here's why Windows 8 will never approach Vista's awfulness | Computerworld Blogs