Actually, if youre watching a DVD movie on a desktop PC, its still possible to multitask. You can just simply pause the movie, minimize Windows Media Center or Windows Media Player for a while and get back to other tasks you were working on the desktop and come back to maximize the media player to fullscreen again. Or when you're gaming, you can just ALT+Tab, then it hides the game screen taking you back to the Desktop to do something else, then just click to the game's button on the taskbar and bingo, it takes you back to the fullscreen game.
Microsoft could easily improve how they display the list of installed programs on the Add/Remove Programs section on the Control Panel without the need for Metro. They could put description on every installed program so its easier to know what they are for. Its not hard for them to tweak how its listed there at all. I think they have done so many improvements on the Control Panel if you compare Windows XP and Windows 7. I suggest that you do not underestimate average users. As I said before, some of them have learned to tidy those up. If MS wanted, they could have easily devised a way in the Control Panel to group apps and to know which are not essential or not frequently used.
Maybe what ADRz meant when he said desktop gadgets are "free" was that besides the Windows 7 license, some gadgets come preinstalled (some Metro apps are preinstalled too) and there are hundreds available for download that are openly shared by those who made them without asking for any money so in description, they can be shareware, open source or freeware. You pay for the OS license of course but you don't pay for these shareware, open source or freeware things that you put into your machine.
In the same sense, when Windows 8 is officially released, you will also need to pay for its license so you could use it and that involves the Metro apps too. You don't pay for the preinstalled Metro apps but you pay for the OS license of the OS that contains them.
My proposal would be, why don't they just create a separate button for switching from Desktop to Metro on the taskbar instead of integrating Metro into our beloved Start Menu which people like me who is not a tablet user take for granted. I think more people will be happy with this idea of a separate button for Metro. I suggest that you watch this video:
Systems Administrator Reacts to Windows 8 - YouTube
That is a picture of how some people working on the enterprise level have reacted to Windows 8 and sadly it wasnt good. Maybe MS should again weigh down the advantages and disadvantages of this design for the good of many and themselves. Everything in Windows 8 except Metro, ribbon on Windows Explorer and Secure Boot is really great in my view but seeing this Metro has many desktop users baffled. Many things are just great about Windows 8 but people's first impression hugely affects their interest on this despite of the other good things they don't know yet and I believe that was a fact with Vista. Vista had some nice features over XP but it got buried down by the things people see as bad. I would choose Vista over XP because I've learned to tweak it like disabling the annoying UAC thing that bugs me as I open apps but unfortunately for Vista, many people did not learn to tweak it and yet others did not even try it then just rode the bandwagon on thinking Vista sucked and refused to upgrade from Windows XP. Microsoft learned their misktake there and came back with Windows 7 which is far superior than any MS operating system before it.
Windows 8 is great, really great only if MS designs it in a more acceptable way for most people, it will be a success.