[mtgx]

I still think Samsung has the best idea for such multi-tasking with "Dual-View":

https://www.youtube.com/watch?v=LZ3krff1JCE&feature=yout...

It's not limited to only one column, like in Ubuntu and Windows 8, it splits the apps even, so you can use them fully, and you can even expand or contract one over the other. I think that's a much better implementation.

But Ubuntu's idea for using the phone apps on the side is not too bad either, but that secondary app seems to be meant more as a "companion" app rather than another full app that you want to use in the same time, and give it equal share of the screen (especially on larger screens).