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

• Guest SMP with up to 32 virtual CPUs (VT-x and AMD-V only; see chapter 3.7.2.2 of the user manual)
• Windows guests: ability to use Direct3D 8/9 applications / games (experimental; see chapter 4.8 of the user manual)
• Support for OpenGL 2.0 for Windows, Linux and Solaris guests

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

• Solaris hosts: allow suspend/resume on the host when a VM is running (bug #3826)
• Solaris hosts: loosen the restriction for contiguous physical memory under certain conditions
• Mac OS X hosts: fixed guest PAE
• Linux hosts: kernel module compile fixes for 2.6.31 (bug #4264)
• VMM: fixed occasional guru meditation when loading a saved state (VT-x only)
• VMM: eliminated IO-APIC overhead with 32 bits guests (VT-x only, some Intel CPUs don’t support this feature (most do); bug #638)
• VMM: fixed 64 bits CentOS guest hangs during early boot (AMD-V only; bug #3927)
• VMM: performance improvements for certain PAE guests (e.g. Linux 2.6.29+ kernels)
• VMM: some Windows guests detected a completely wrong CPU frequency (bug #2227)
• VMM: fixed hanging and unkillable VM processes (bug #4040)
• VMM: fixed random infrequent guest crashes due to XMM state corruption (Win64 hosts only)
• VMM: performance improvements for network I/O (VT-x/AMD-V only)
• GUI: added mini toolbar for fullscreen and seamless mode (Thanks to Huihong Luo)
• GUI: redesigned settings dialogs
• GUI: allow to create/remove more than one host-only network adapters (non Windows hosts)
• GUI: display estimated time for long running operations (e.g. OVF import/export)
• GUI: fixed rare hangs when open the OVF import/export wizards (bug #4157)
• 3D support: fixed VM crashes for client applications using incorrect OpenGL states
• 3D support: fixed memory corruption when querying for supported texture compression formats
• 3D support: fixed incorrect rendering of glDrawRangeElements
• 3D support: fixed memory leak when using VBOs
• 3D support: fixed glew library detection
• 3D support: fixed random textures corruption
• VRDP: support Windows 7 RDP client
• Networking: fixed another problem with TX checksum offloading with Linux kernels up to version 2.6.18
• NAT: fixed “open ports on virtual router 10.0.2.2 - 513, 514” (forum)
• NAT: allow to configure socket and internal parameters
• NAT: allow to bind sockets to specific interface
• PXE boot: significant performance increase (VT-x/AMD-V only)
• VHD: properly write empty sectors when cloning of VHD images (bug #4080)
• VHD: fixed crash when discarding snapshots of a VHD image
• VHD: fixed access beyond the block bitmap which could lead to arbitrary crashes
• VBoxManage: fixed incorrect partition table processing when creating VMDK files giving raw partition access (bug #3510)
• VBoxManage: support cloning to existing image file
• OVF: several OVF 1.0 compatibility fixes
• OVF: fixed exporting of disk images when multiple virtual machines are exported at once
• Virtual mouse device: eliminated micro-movements of the virtual mouse which were confusing some applications (bug #3782)
• Shared Folders: sometimes a file was created using the wrong permissions (2.2.0 regression; bug #3785)
• Shared Folders: allow to change file attributes from Linux guests and use the correct file mode when creating files
• Shared Folders: some content was incorrectly written under certain conditions (bug #1187)
• Shared Folders: fixed incorrect file timestamps, when using Windows guest on a Linux host (bug #3404)
• X11 clipboard: fix duplicate end of lines (bug #4270)
• X11 guests: a number of shared clipboard fixes
• Linux guests: Guest Additions support for SUSE Linux Enterprise Desktop 11
• Linux guests: new daemon vboxadd-service to handle time synchronization and guest property lookup
• Linux guests: implemented guest properties (OS info, logged in users, basic network information)
• Windows host installer: VirtualBox Python API can now be installed automatically (requires Python and Win32 Extensions installed)
• USB: Support for high-speed isochronous endpoints has been added. In addition, read-ahead buffering is performed for input endpoints (currently Linux hosts only). This should allow additional devices to work, notably webcams (bug #242).
• USB: fixed error handling for some USB dongles
• Web service: fixed inability to handle NULL pointers for object arguments, which are valid values for a lot of APIs, in both the raw and the object-oriented web service.
• Web service: object-oriented bindings for JAX-WS did not exhibit interface inheritance correctly, fixed
• Web service: added support for IDisplay and IGuest interfaces, which were previously unavailable