Network Performance Analysis in a virtualized environment like VMware can be a tricky beast as often times everything is encapsulated using GRE tunnels between virtual switches. What can we do? As luck would have it, most virtual switches support Netflow. Yes, vSphere NetFlow support is available.
You probably already have the ability to export Net flow from your Virtual switches. VMware supports Netflow V5 for Network monitoring. Also OpenVSwitch NetFlow is now available and the Nexus 1000V will export to your NetFlow collector as well. 
I am not aware of any performance metrics such as latency, jitter, packet loss etc… that can be natively exported out of a virtual environment, however, in that situation I would consider spanning a virtual port on a virtual switch to an nBox which exports IPFIX (NetFlow) with this next generation performance information.
We covered examples of these types of next generation performance metrics using NetFlow in our webcast on Cisco Performance Monitoring. Check it out!