I think you misread my post or I just didnt explain myself properly
, what I meant was that proper metro apps will be based for tablets/phones hence the initial fullscreen BAM type stuff, it needs refinement but you can make metro apps not fullscreen, simply open them and move your mouse to the top of the screen (will turn to a hand icon) then drag it to where you want it, if you want to side load applications simply hover over the left side and right click the app tile and click snap left/right.
Im not saying its a good idea but i meant that in the realm of tablets/phones you have limited space so you will do things one at a time but leaving them running in the background is fine e.g. a voice skype call you can leave running while you browse the web etc.
Desktop side is fine, just dont use metro apps
. It needs improving for desktops but apart from that its got the right idea for mobile devices.