Others haven’t given much of visibility for this function, but i consider this to be very important for the daily use of the UI. Just like on N900 the N9/N950 will get laggy as apps pile up. We are talking about live multitasking after all, especially when you got heavy apps running on the background like maps it’s important that you can close it right away when that one visit is enough. I’m also a bit pedantic on keeping the multitasking view on N900 clean with only apps i need. 
Being able to close the app by swiping from top to bottom of the screen was confirmed by known Nokia workers already, but not yet demonstrated. To get this function working you need to enable it from settings, or that at least was the case month ago. According to guy who told about this for me for the first time it was done to not confuse novice users.
