The new dashboard comes with many new features that I think everyone will love. First is an all new visual layout that resembles the Metro UI found on Windows phones and the upcoming Windows 8.
Second; Microsoft is bringing a Bing like search to the dashboard that will make it way easier for you to find what you are looking for on the Xbox Marketplace.
The Dashboard update will also sport newly added 'beacons' which allow players to tell others what and if they want to play a game, this should avoid annoying invites when playing Alan Wake for instance.
And finally for now, Microsoft is bringing a big white fluffy cloud to the Xbox that will store your Xbox LIVE profile and game saves. Making it easier for you to load your account up at friends houses.
We have to still wait for the inclusion of the TV and movie applications until further notice though.
Ronnie W
Andreas R 
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Aaron W 
I'm a PlayStationer and never intend to get an Xbox, but I gotta say this new dash looks very nice. This new Xbox dash is simplistic and easy on the eye. I wish Sony would add some depth and personality to the XMB while keeping it simple; it's as if their firmware team is all coders and no designers.