Yes, yes it is.
We are very excited about hitting this stage of development, and while there's more work yet to be done, we're very happy to finally get the product into the hands of the larger customer base.
Can we run Beta 3 in production?
The official answer is that you may run this beta release on public sites, but we don't recommend it. If you put it in production, make sure to back up all of your data and files before upgrading.
Please remember that there is no official support for vB4 until the Gold release, so if you decide to put it in production, you're taking all of the usual risks of using beta-stage software. This means that there are still known bugs, some of which might be significant to your members, depending on how they use the software.
Is there anything we should be especially careful of?
New, fresh installations have been relatively predictable, but we have experienced some potentially serious issues upgrading existing vBulletin installations, depending on customization, configuration and certain aspects your database. In particular, disable all of your plugins before attempting upgrades.
Some things to check before upgrading, especially if you are setting up a test site from a copy of your production site.
1) Make sure that the forum URL setting is correct.
2) If attachments are stored on the file system, make sure that the test site points to a valid attachment directory that is different from the production site's directory.
3) Make sure that any attachment files from the production site get copied to the test site directory.
Where do we report bugs?
In the usual bug tracker - here.
Will my existing styles and plug-ins work?
Please see this FAQ entry.
When will the gold release be?
The Gold release will come once all of our release criteria have been satisfied. At this time, we expect Gold to be released before the end of the year.