It's probably stable and featured enough to be full release, however I am too tired to wait for a PGO build. If you want the absolute best performance, use the previous build.
Classic gradient for readable text and icons was fixed. This was apparently broken in 115 ESR and something in 125 partially fixed it somehow.
Lightweight themes coloring tab bar should* work now.
Bookmarks menus are now native(ish), the weird border has been removed.
Text boxes looking off is fixed.
JPEG XL is enabled by default.
More telemetry removed.
More branding adjustments.
Install/uninstall ping should be removed.
Uninstaller no longer asks for telemetry.
GPU acceleration in VM should work now assuming it meets all other prerequisites.