OCR works fine on Big Sur but not yet on ARM-based Macs due to an issue of the Abbyy engine. The next release will also fix some minor glitches and update the toolbars for Big Sur. And the Mail plug-in hasn’t been updated yet but there are several alternatives (e.g. drag & drop, scripts and View > Sidebar > Import).
But as usual I would highly discourage to update to a .0 release of macOS in a production environment, at least as long as you’re not a developer and need it for your work 