Dmitri is a Solution Architect within the NSBU at VMware. I am very lucky to have him within my office so I can annoy the heck out of him. He is an exceptionally talented person who gets it at the big picture and can drill down into the minutiae.
He just published a very detailed post over on his blog about how NSX performs ARP suppression. It gives a good insight into what the controller does in Unicast mode and some great commands to troubleshoot.