We just announced RC1 on the dev blog.  The only change since Beta 1 was a small fix to wp-mail.php to address ticket #5169.  If there are no unpleasant surprises, the final 2.3.1 release should be out in the next day or two.

WordPress 2.3.1, the first maintenance release for the 2.3 series, is coming out soon. The first beta is available now. Get it here.

Over twenty bugs are fixed in 2.3.1. Get the full list here. Here are some highlights.

• Tagging support for Windows Live Writer
• A login bug that affected those with a Blog Address different than
  their WordPress Address is fixed
• Faster taxonomy database queries, especially tag intersection queries
• Link importer fixes

The standard disclaimer for beta software applies. Please report any bugs you find on the bug tracker.