I have to agree, I have setups where we have 4 servers all on the same vswitch and the transfer rates are slower than what I would expect copying across the network. Latest version with all of the patches.
Also for example when we are upgrading a server we always virtualise the old server first to the new box in the aim that transferring the data to the new server will be very fast onthe same vswitch and its safe to say this is not the case, copying still takes an age as if it was across a network.