I will admit that it is pretty tough making it to early sessions here in Vegas! I did manage to catch Joseph Dieckhans' session on Troubleshooting Storage performance with vSphere 5. He had a lot of essential information that all admins should be aware of when troubleshooting storage. For years I have always used esxtop to troubleshoot issues and that is still the case today. Joe did show a nice slide of vCenter ops that can give you the same detailed information. Vscsi stats is also a great tool for troubleshooting storage. Joe's presentation gave a great overview of kavg = gavg – davg for looking into latency issues. These are values read in esxtop. There are also circumstances where you may need to dive into the OS of the VM to tune performance when nothing is found in the VMWare or hardware stack.