Update:
A second video has been posted which demos email notification in Glance screen and more of new multitasking UI.
The same person who has earlier posted screenshotsfrom his developer edition Lumia 920 running GDR3 and Lumia Bittersweet Shimmer update has now posted a video demo of the features. Though this is a brief demo but still confirms what has been earlier posted in screenshots.
[embedit snippet=”madsr”]