This is true multi tasking!

Here is a short video of how even a minimised browser window with a you tube video running will continue to play and zero lag or device slowdown.

You can also see how images on the minimised people app scroll on the minimised "tile".  This is similar to Windows phone tile, which is not always a bad thing.

Please excuse the video being on its side but Windows 7 was having a hissy fit every time I tried to rotate it in movie maker so I left as is in the end.