Have a customer that we just installed new 6035 nodes using the Haswell chip. Found that they had an issue where CVM network latency checks would periodically fail. Inspecting the log with support showed occasional 70ms+ spikes both for CVM-to-CVM and CVM-to-gateway settings.
This is a vSphere 5.5 U2 cluster, so we set the power settings for high-performance instead of balanced (default by foundation) and the latency issue went away. We're guessing there is some new ACPI tweaks required by VMware for ESXi. After configuring high performance, the latency between CVMs went from .2 to .3 millisecond average (typical) to more in the .07 - .09 range, and so far we're no longer observing any big spikes.