According to Sun, the newest major featured added are:
- 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 an arbitrary IDE controller, 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)
The first of these new features, 'Teleportation', is HUGE. The ability to migrate a live virtual machine really makes downtime a think of the past and the true multi-platform nature of VirtualBox (Solaris, Linux, Mac and Windows), allows for this migration to take place across operating systems, hardware vendors, processor architectures and even from servers to clients.
Allowing restores from arbitrary snapshots makes for a pseudo revision control system for virtual machines. This is a definitely a feature that will come in handy for developers and testers.
2D video acceleration will definitely help on the virtual desktop front. Flexible storage attachments allow users to more accurately mimic physical hardware for certain systems, and changing a network attachment type on-the-fly can help with virtual network testing. The rewrite of USB drivers for OpenSolaris brings the platform closer to plug and play functionality.
A performance increase for PAE and AMD64 guests is always a welcome thing as is the foray into EFI support. Naturally, the paravirtualized network driver will drastically increase networking performance for guests.
I would say that Sun has made some major advancements overall in their flagship virtualization platform. Having used VirtualBox on several machines with Unix, Linux, Mac and Windows in my lab, I can definitely attest to the speed and usability of the platform. The added ability to migrate my virtual machines across all of my hosts is a very welcome addition. Paired with SunRay Software 5, I can see the newest release of VirtualBox serving as a solid foundation for a Desktop VDI platform.