Steam Big Picture!
Woah! Steam just updated and there is a large button top right called "The Big Picture", clicking on said button turns steam into a Windows Media Centre/XBbox 360 style interface!
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Seems Valve are aiming to move into the front room as well? :)
I tried it and it probably does make more sense with a remote/gamepad. Maybe PS3 will see this interface at some point? (MS threw a hissy and wouldn't let them have Steam on XBL).
A number of interfaces such as friend profiles are just a full screen web page mind you, the same as what you get on normal Steam, making it fairly pointless.