The Halo 3 beta is now live to those who have been invited to participate, however people hoping to get in through their purchase of Crackdown are still waiting due to technical difficulties.
The official statement from the Bungie.net homepage currently reads:
"
With any luck this will be a short delay. People entering the Beta through other methods - Friends and Family, Rule of Three and so on, are unaffected."
While that on GamerScoreBlog is as follows:
"
Bungie and the Xbox LIVE team are aware there are issues downloading the beta via Crackdown. They're working on the issue, and they expect everything to be up and running soon. Frankie's on point to keep everyone updated, so as soon as there's news, you'll find it on www.bungie.net."
Let's hope for a speedy resolution! In the meantime you can check out Bungie's Official Halo 3 Beta Guide
here. It contains everything from map guides, to weapons and vehicles, equipment and networking info. The demo is 911.17MB in size.
