The OpenNebula 4.0 release offers up various new Virtual Machine features, scheduler improvements, a re-designed administration interface, and worthwhile enhancements to many of its other subsystems.
Among the new VM functionality is that for disk snapshoting, capacity resizing, programmable actions, and IPv6, are the changes mentioned in the release notes. There's also new drivers like with Ceph and then the usual improvements for VMware, KVM, and Xen.
More details on OpenNebula 4.0 can be found from the project release announcement. A video showing off the new Sunstone web interface and other features is embedded below.