Or at least have the user set which will be their default. I think Metro is actually fine for most users who are only using web, email, media, etc. even if on their laptops (yes, their are many people who fall into this category).
I find I'm in the desktop most of the time and almost never go to the metro start screen, which is a shame, because I'd like to be able to use their innovations, but most of the apps I run only run in desktop mode.
I like Windows 8, but I really just like using it on touchscreen devices. On a touchscreen device, I think it has the potential to dominate everything else, as long as the apps start to show up and the second round of devices isn't plagued by crippling hardware and software defects, like nearly everything that wasn't manufactured by Microsoft.
The best way I can describe using the new interface on a non-touch device is that it feels like the operating system equivalent of a console port.
I find I'm in the desktop most of the time and almost never go to the metro start screen, which is a shame, because I'd like to be able to use their innovations, but most of the apps I run only run in desktop mode.