The part I don’t think people really get is that if your goal was to have a fork of RHEL that was as close as possible to RHEL itself in absolute value that CentOS Stream is much better than CentOS is/was. CentOS always tracked far behind RHEL and now CentOS Stream will track closely in front of RHEL.
And I only recall CentOS significantly trailing RHEL at the major version updates (e.g. 6 and 7). Other updates seem pretty timely, and the major version lag doesn't leave me vulnerable.
I can see this being useful for developers who are building something that needs to be compatible with the next major release of RHEL, but I'm not sure who else it will be useful for.
Unless you're the kind of person who pinned to a specific minor version of CentOS (which isn't the default and not supported for very long) you can use CentOS Stream exactly the same as you currently are and it will be a strict improvement for you. Bugfixes, security updates, and new features will come to you before they're either batched for release in the next minor version of RHEL or back-ported to the current supported releases.
I'm sure they'll try not to break binary compatibility, but as it appears to be somewhat experimental and targeted to developers, breaking updates may occur. Isn't that the point of this distro -- so such testing can take place before updates are rolled into RHEL?
So, fine for a developer workstation, but I don't see how it can be stable enough to use in production.
Security fixes are not coming to CentOS Stream first. That's been in the announcement.