Samsung has been a leader in multitasking with Touchwiz's mutliwindow feature. With multiwindow you are able to do a few things at once like watch a video while typing an email, or read twitter while listening to youtube music. Multitasking on Android can be a huge boost to productivity. The Multiwindow feature may be coming to Android soon. A commit was pushed to the Android Open Source Project which mentions the feature several times. This would be an awesome feature for stock android. Currently you have to root your device to get a mod to do the same thing. Hopefully this will be added sooner than later.
via googlesource