The thing is there is a non-trivial number of computer users that used Win9x extensively and then 2000/XP and everything else after that who are used to that "old GUI". Honestly I think that old GUI is much better suited to any task that is complex enough to require the user to operate multiple different applications together to achieve a higher goal. I suspect that your teenage daughter's most complex computing task is typing her school papers. She probably doesn't create a whole lot of diagrams and pictures to go with them so she probably only ever has to look at Word and not do any context switching.
Really the users that do complex work flows involving multiple applications at once are Microsoft's core audience which for whatever reason they seem to have mostly forgotten about. Just to put things in to perspective, that kind of user is often referred to as a "power user" now... I remember when the term power user meant something meaningful.
And the thing is, it would be sooooo easy for Microsoft to make the "power users" happy. Here are the simple changes that would make everyone love Win8:
1. Bring the Start Menu back as an option. You don't have to make it the default, just make it an option.
2. Optionally allow Metro apps to run in a window on the desktop
3. Optionally allow the user to disable the charm bar
4. Allow the user to select between the Win8 Modern theme, Win7 Aero theme, or Windows classic theme.
Give the user the choice of how he/she wants the GUI to look and everyone will flock to Win8. It seems that Microsoft has forgotten one of Bill Gate's most important lessons, the power of the default.
If anyone from Microsoft is reading this, really guys please do this. The PC industry is in the shitter right now because of your arrogance NOT because of the iPad. The entire industry including you and including me would be better off if people started buying PCs again instead of $150 android tablets, the typical ~$400 PC + new software licenses to go along with it pumps a lot more money in to just about everyone's pocket (except maybe Apple and Google).