“The participation in the ‘Halo 3’ beta was staggering,” said Shane Kim, corporate vice president of Microsoft Game Studios. “Witnessing such a great reaction to a small portion of the game has been inspiring. It’s a testament to the fervor and anticipation that surrounds ‘Halo 3.’ We’re confident that on Sept. 25 Halo 3 will drive an unprecedented wave of new gamers to the Xbox 360 platform and Xbox LIVE.”
In a press release issued today, they announced various pieces of hardware that will be coupled along with the game to spur sales, as well as shedding some light on what all the beta assisted development with. During the course of the beta, over 580,000 films of gameplay were recorded by users and saved via Xbox LIVE, which apparently Bungie will use to improve the game.
820,000 participants in less than a month of beta is pretty good, and gives a good indication of how well the game will sell upon official release. You can read the full press release at Microsoft's site.