Update: It appears that space has been full. Here’s a quote from major nelson: We’ve had an overwhelming demand for participation, and have closed registration.
If we re-open registration, I’ll let you know
If you have an Xbox 360 and love testing the cutting-edge software, I have good news for you! You sign up for the beta program for your Xbox 360 this summer. This beta program will let you have an early download of the Xbox 360 dash board update that is coming this fall.
Space is limited, and, thus, you need to sign up for the beta BEFORE it is full. You can do this only form your Xbox 360 dashboard home screen. On the home screen, you will have an option to sign up for the beta. If you choose to do so, you will be prompted to install a small app for your Xbox. After you install the app, you will need to select the option to sign up for the beta again from the Xbox 36t0 home screen. This will launch the sign-up utility. Just follow the on-screen instructions to join the beta. Hurry because it’s filling up fast!
I do wander if we will see a UI change in this next update to match that of the UI shown off for the Xbox One. The Xbox One dashboard features a nicer looking dark background with bright tiles. It does look nicer than the current Xbox 360 dashboard. But we shall shee.
Source: Major Nelson