AT&T's demonstration video for the Xbox 360 U-Verse service
(after the break) gives us a better idea of how the service works -- and what's in the mysterious hardware kit (a remote and some kind of receiver device). The presenter also describes the installation process, wherein the U-verse software is installed on the 360 via a CD, a process described as "super-easy." ProTip, AT&T: don't tell us that the installation we have to pay $55 for is "super-easy."
The interface shown in the video looks exactly like the UI for a normal U-verse receiver. The only perceptible difference, of course, is the appearance of Xbox Live notifications.