This version is a major update. The following major new features were added:

• Following the acquisition of Sun Microsystems by Oracle Corporation, the product is now called Oracle VM VirtualBox and all references were changed without impacting compatibility
• Experimental support for Mac OS X Server guests (see the manual for more information)
• Memory ballooning to dynamically in- or decrease the amount of RAM used by a VM (64-bit hosts only) (see the manual for more information)
• Page Fusion automatically de-duplicates RAM when running similar VMs thereby increasing capacity. Currently supported for Windows guests on 64-bit hosts (see the manual for more information)
• CPU hot-plugging for Linux (hot-add and hot-remove) and certain Windows guests (hot-add only) (see the manual for more information)
• New Hypervisor features: with both VT-x/AMD-V on 64-bit hosts, using large pages can improve performance (see the manual for more information); also, on VT-x, unrestricted guest execution is now supported (if nested paging is enabled with VT-x, real mode and protected mode without paging code runs faster, which mainly speeds up guest OS booting)
• Support for deleting snapshots while the VM is running
• Support for multi-monitor guest setups in the GUI for Windows guests (see the manual for more information)
• USB tablet/keyboard emulation for improved user experience if no Guest Additions are available (see the manual for more information).
• LsiLogic SAS controller emulation (see the manual for more information)
• RDP video acceleration (see the manual for more information)
• NAT engine configuration via API and VBoxManage
• Use of host I/O cache is now configurable (see the manual for more information)
• Guest Additions: added support for executing guest applications from the host system (replaces the automatic system presimparation feature; see the manual for more information)
• OVF: enhanced OVF support with custom namespace to preserve settings that are not part of the base OVF standard

In addition, the following items were fixed and/or added:

• VMM: fixed Windows 2000 guest crash when configured with a large amount of RAM (bug #5800)
• Linux/Solaris guests: PAM module for automatic logons added
• GUI: guess the OS type from the OS name when creating a new VM
• GUI: added VM setting for passing the time in UTC instead of passing the local host time to the guest (bug #1310)
• GUI: fixed seamless mode on secondary monitors (bugs #1322 and #1669)
• GUI: offer to download the user manual in the OSE version (bug #6442)
• GUI: allow to set an empty host key to disallow any host key combination (bug #684)
• GUI: allow to restrict the possible actions when shutting down the VM from the GUI
• Main: allow to start a VM even if a virtual DVD or floppy medium is not accessible
• Settings: be more robust when saving the XML settings files
• Mac OS X: rewrite of the CoreAudio driver and added support for audio input (bug #5869)
• Mac OS X: external VRDP authentication module support (bug #3106)
• Mac OS X: Moved the realtime dock preview settings to the VM settings (no global option anymore). Use the dock menu to configure it.
• Mac OS X: added the VM menu to the dock menu
• 3D support: fixed corrupted surface rendering (bug #5695)
• 3D support: fixed VM crashes when using ARB_IMAGING (bug #6014)
• 3D support: fixed assertion when guest applications uses several windows with single OpenGL context (bug #4598)
• 3D support: added GL_ARB_pixel_buffer_object support
• 3D support: added OpenGL 2.1 support
• 3D support: fixed Final frame of Compiz animation not updated to the screen (Mac OS X only) (bug #4653)
• 3D support: fixed blank screen after loading snapshot of VM with enabled Compiz
• Added support for virtual high precision event timer (HPET)
• OVF: fixed mapping between two IDE channels in OVF and the one IDE controller in VirtualBox
• OVF: fix VMDK format string identifiers and sort XML elements from rasd: namespace alphabetically as prescribed by standard
• VBoxShell: interactive Python shell extended to be fully functional TUI for VirtualBox
• Linux Additions: support Fedora 13 (bug #6370)
• VBoxManage: fixed overly strict checks when creating a raw partition VMDK (bugs #688, #4438)