New major features
- OVF (Open Virtualization Format) appliance import and export (see chapter 3.8, Importing and exporting virtual machines, User Manual page 55)
- Host-only networking mode (see chapter 6.7, Host-only networking, User Manual page 88)
- Hypervisor optimizations with significant performance gains for high context switching rates
- Raised the memory limit for VMs on 64-bit hosts to 16GB
- VT-x/AMD-V are enabled by default for newly created virtual machines
- USB (OHCI & EHCI) is enabled by default for newly created virtual machines (Qt GUI only)
- Experimental USB support for OpenSolaris hosts
- Shared folders for Solaris and OpenSolaris guests
- OpenGL 3D acceleration for Linux and Solaris guests (see chapter 4.8, Hardware 3D acceleration (OpenGL), User Manual page 70)
- Added C API in addition to C++, Java, Python and Web Services

Other additions, changes or bug fixes
VMM: FreeBSD guest related fix for V86 flags (bug #2342)
VMM: fixed guru meditation when booting an AsteriskNow Linux VM (bug #2342)
VMM: fixed PGMPOOLKIND_FREE guru meditation (bugs #3356, #3431)
VMM: fixed Windows XP boot hang (guest PAE + nested paging only)
VMM: allow mixing of VT-x/AMD-V and software virtualization
VMM: fixed extremely slow safe mode booting in e.g. Windows 2008 (VT-x/AMD-V only)
VMM: significant speedup of certain GRUB boot loaders (e.g. Solaris) (VT-x/AMD-V only)
VMM: real-mode IOPL fix for DOS guests (VT-x only)
VMM: fixed VT-x detection with certain BIOSes that enable VT-x, but don’t set the lock bit in MSR_IA32_FEATURE_CONTROL
VMM: fixed hibernation issues on Windows XP hosts (VT-x only; bug #1794)
VMM: properly emulate RDMSR from the TSC MSR, should fix some NetBSD guests
VMM: emulate RDPMC; fixes Windows guests crashes when using the Kaspersky virus scanner (bug #1778)
NAT: fixed truncated downloads (FTP) (bug #3257)
NAT: blocked UDP packets caused a crash (bug #3426)
NAT: allow to configure the next server and the boot file via VBoxManage (bug #2759)
IDE: fixed hard disk upgrade from XML-1.2 settings (bug #1518)
Hard disk: support more VMDK file variants (including fixed-size ESX server images)
Hard disks: refuse to start the VM if a disk image is not writable
USB: further reduced host CPU utilization for OHCI and EHCI; the “VBoxInternal/Devices/usb-ohci/0/Config/FrameRate” CFG key is no longer necessary and no longer supported
USB: fixed BSOD on the host with certain USB devices (Windows hosts only; bug #1654)
E1000: properly handle cable disconnects (bug #3421)
VRDP: fixed hangs when VRDP server is enabled or disabled in runtime
Shared folders: respect umask settings on Linux, OSX and Solaris hosts when creating files
X11 guests: prevented setting the locale in vboxmouse, as this caused problems with Turkish locales (bug #3563)
X11 guests: show the guest mouse pointer at the right position if the virtual desktop is larger than the guest resolution (bug #2306)
Linux additions: fixed typo when detecting Xorg 1.6 (bug #3555)
Solaris guests: added xpg4/xcu4 dependency to the guest additions installer (bug #3524)
Windows guests: bind the VBoxMouse.sys filter driver to the correct guest pointing device (bug #1324)
Windows hosts: fixed BSOD when starting a VM with enabled host interface (bug #3414)
Linux hosts: do proper reference counting to prevent unloading the vboxnetflt module as long as this code is in use (bug #3104)
Linux hosts: do not leave zombies of VBoxSysInfo.sh (bug #3586)
Linux installers: fixes for Slackware, Arch Linux and Linux from Scratch systems
Windows installers: combined installer executable which contains both (32- and 64-bit) architectures.
VBoxManage: less cryptic command-line error messages
VBoxManage list vms commands now default to compact format
VBoxManage controlvm dvdattach did not work if the image was attached before
VBoxManage: allow creation of all supported disk image variants
VBoxManage showvminfo: don’t spam the release log if the additions don’t support statistics information (bug #3457)
VBoxManage: big command line processing cleanup, the legacy single-dash options are deprecated and will be removed in the next major release, so switch to the new options now
Hard disks: improved immutable disk support to auto-reset diff file at VM startup (related to bug #2772)
GUI: enable the audio adapter by default for new VMs
GUI: warn if VT-x/AMD-V is not operational when starting a 64-bit guest
GUI: deactivate 64-bit guest support when the host CPU does not support VT-x/AMD-V
GUI: removed floppy icon from the status bar
GUI: show build revision in about dialog
GUI: fixed sticky status bar text
GUI: improved error dialogs
GUI: fail with an appropriate error message when trying to boot a read-only disk image (bug #1745)
GUI/Mac OS X: fixed disabled close button
GUI/Windows: re-enabled support for copy and paste (Windows hosts 2.0 regression; bug #2065)
3D support: added OpenGL select/feedback support (bug #2920)
3D support: close OpenGL subsystem for terminated guest applications (bug #3243)
3D support: fixed VM hangs when starting guests with 3D acceleration enabled (bug #3437)
PXE: fixed boot hangs when hardware virtualization is used (bug #2536)
LsiLogic: fixed problems with Solaris guests
Main API: close machine settings XML file when unregistering machine (bug #3548)