This beta version is the first official release of the Colorbox module for Drupal 7. I have tested it against the just released Drupal 7.0 and it seems to work well for me.
Please try it out and report any problems to the issue queue.
We are not far from a stable release. Thanks to contribution, testing and suggestions from users recrit, gooddesignusa and several others this module is getting really nice indeed.
The biggest thing in this beta is a much improved support for the Image module thanks to patches from recrit.