Hyper-V Virtual Switch in Windows Server 2012 R2 has a lot of great new features that provide security, performance, and compatibility improvements.
One of the best improvements is that the switch now peacefully coexists with third party forwarding extensions, and performs hybrid forwarding. With hybrid forwarding, network traffic that is Network Virtualization Generic Routing Encapsulation (NVGRE) encapsulated is forwarded by the HNV module within the switch, while all non-NVGRE network traffic is forwarded by the third party forwarding extensions that you have installed.
Also new is Extended Port Access Control Lists (ACLs), which allow you to create granular firewall rules to block or allow specific protocol traffic to and from VMs that are connected to the switch. Extended ACLs also now allow you to configure stateful rules that are unidirectional and provide a timeout parameter.
For more information on these and other new Hyper-V Virtual Switch features, see What's New in Hyper-V Virtual Switch for Windows Server 2012 R2 at http://technet.microsoft.com/library/dn343757.aspx.