Windows 7, on its own merits, isn't bad - but sadly it's what Vista should have been 7 or 8 years ago, and it still doesn't boast all the improvements Microsoft bragged it would (multiple pop-ups doesn't equal stronger security, and the "Aero" interface doesn't mean better functionality).
The problem I have is when they make erroneous comparisons to OS X; And yes, I realise this is advertising and to be expected, but it still gets under my skin. They base all or most of their (lame) arguments around the fact Windows has a dominant market share - which means nothing compared to actual quality of the product. And as Macintosh market share increases, these arguments will see their validity decrease.
Ultimately, if you use Windows 7, or are forced to use a Windows machine for work, etc, Windows 7 isn't bad. But it is not the same quality as Macintosh.