- Over 20 Kickstart ROM modules and many more disk-based core OS components were fixed, updated, or added.
- Native support for all Motorola 68000-68060 CPUs, and a more robust Auto-Configuration process.
- Support for large hard disks, including boot, for any OS 2.x/3.x-compliant controller driver supporting HD_SCSI_CMD, TD_64 and/or NSD. Dedicated boot partitions are a thing of the past, even on legacy devices. You can also use variably-sized "super floppies".
- A modernized Workbench as powerful as the OS 3.9 version, including new or refreshed Preference editors in the legacy OS 3.1-"GadTools" style. Its tools such as DiskCopy and Format fully support large media. Printer, hard disk and many other support tools have been fixed and upgraded.
- Remember "Diskdoctor"? It earned its PhD and is now ready to reliably rescue data from your floppies or hard disks.
- The CLI/Shell and many of its commands have been reworked and modernized, now sporting native support for pipes, softlinks, hardlinks and long filenames. New commands support running Workbench programs from the Shell or upgrading ROM modules.
- CrossDOS and the CD-ROM filesystem are now smarter, faster, and multi-threaded, adding Rockridge and Joliet extensions as well as UDF.
- Fully reworked, modernized and bug-fixed printer drivers include support for PCL and PostScript, along with legacy NEC and Epson printers.
- An optional, upgradeable intuition.library provides off-screen dragging of windows for native and Picasso96 RTG screens.
- A colorful, professionally-designed icon set is included, along with the traditional four-color icons.