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

* Teleportation (aka live migration); migrate a live VM session from one host to another (see the manual for more information)
* VM states can now be restored from arbitrary snapshots instead of only the last one, and new snapshots can be taken from other snapshots as well ("branched snapshots"; see the manual for more information)
* 2D video acceleration for Windows guests; use the host video hardware for overlay stretching and color conversion (see the manual for more information)
* More flexible storage attachments: CD/DVD drives can be attached to arbitrary storage controllers, and there can be more than one such drive (the manual for more information)
* The network attachment type can be changed while a VM is running
* Complete rewrite of experimental USB support for OpenSolaris hosts making use of the latest USB enhancements in Solaris Nevada 124 and higher
* Significant performance improvements for PAE and AMD64 guests (VT-x and AMD-V only; normal (non-nested) paging)
* Experimental support for EFI (Extensible Firmware Interface; see the manual for more information)
* Support for paravirtualized network adapters (virtio-net; see the manual for more information)

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

* VMM: guest SMP fixes for certain rare cases
* GUI: snapshots include a screenshot
* GUI: locked storage media can be unmounted by force
* GUI: the a log window grabbed all key events from other GUI windows (bug #5291)
* GUI: allow to disable USB filters (bug #5426)
* GUI: improved memory slider in the VM settings
* GUI: the VirtualBox website couldn't be opened from the help menu (bug #4559)
* 3D support: major performance improvement in VBO processing
* 3D support: added GL_EXT_framebuffer_object, GL_EXT_compiled_vertex_array support
* 3D support: fixed crashes in FarCry, SecondLife, Call of Duty, Unreal Tournament, Eve Online (bugs #2801, #2791)
* 3D support: fixed graphics corruption in World of Warcraft (#2816)
* 3D support: fixed Final frame of Compiz animation not updated to the screen (#4653)
* 3D support: fixed incorrect rendering of non ARGB textures under compiz
* iSCSI: support iSCSI targets with more than 2TiB capacity
* VRDP: fixed occasional VRDP server crash (bug #5424)
* Network: fixed the E1000 emulation for QNX (and probably other) guests (bug #3206)
* NAT: added host resolver DNS proxy (see the manual for more information)
* VMDK: fixed incorrectly rejected big images split into 2G pieces (bug #5523, #2787)
* VMDK: fixed compatibility issue with fixed or raw disk VMDK files (bug #2723)
* VHD: fixed incompatibility with Hyper-V
* Support for Parallels version 2 disk image (HDD) files; see the manual for more information
* OVF: create manifest files on export and verify the content of an optional manifest file on import
* OVF: fixed memory setting during import (bug #4188)
* Mouse device: now five buttons are passed to the guest (bug #3773)
* VBoxHeadless: fixed loss of saved state when VM fails to start
* VBoxSDL: fixed crash during shutdown (Windows hosts only)
* X11 based hosts: allow the user to specify their own scan code layout (bug #2302)
* Mac OS X hosts: don't auto show the menu and dock in fullscreen (bug #4866)
* Mac OS X hosts (64 bit): don't interpret mouse wheel events as left click (bug #5049)
* Mac OS X hosts: fixed a VM abort during shutdown under certain conditions
* Solaris hosts: combined the kernel interface package into the VirtualBox main package
* Solaris hosts: support for OpenSolaris Boomer architecture (with OSS audio backend).
* Shared folders: VBOXSVR is visible in Network folder (Windows guests, bug #4842)
* Shared folders: performance improvements (Windows guests, bug #1728)
* Windows, Linux and Solaris Additions: added balloon tip notifier if VirtualBox host version was updated and Additions are out of date
* Solaris guests: fixed keyboard emulation (bug #1589)
* Solaris Additions: fixed as_pagelock() failed errors affecting guest properties (bug #5337)
* Windows Additions: added automatic logon support for Windows Vista and Windows 7
* Windows Additions: improved file version lookup for guest OS information
* Windows Additions: fixed runtime OS detection on Windows 7 for session information
* Windows Additions: fixed crash in seamless mode (contributed by Huihong Luo)
* Linux Additions: added support for uninstalling the Linux Guest Additions (bug #4039)
* Linux guest shared folders: allow mounting a shared folder if a file of the same name as the folder exists in the current directory (bug #928)
* SDK: added object-oriented web service bindings for PHP5