For those who can't play the beta try this, Bungie said that there's some bug in the beta:

From bungie.net:

Note : A rare bug has been discovered that sometimes results in improper text display in the game UI. Basically, you won't see any text at all. If you encounter this issue, you can fix it yourself by doing the following:

1. Restart your Xbox 360
2. Boot up the Halo 3 Beta
3. While the Halo 3 Beta is loading, immediately press up on the D-Pad and hold the A button until you see the Bungie logo. If you perform this correctly a dialog box will appear confirming maintenance has been done to your system.
4. Resume the Halo 3 Beta!

Depends on what you are looking for. Rainbow Six 3 has the best single player campaign by far. Black Arrow has the better multiplayer with more features.neutralx2