The HTML5 interface is very nice. The flash interface was better in 6.5 over 6.0 but it is still flash. I use the HTML5 interface for must of my work but it is missing some key features, 6.5 update 3 added a lot of them into the interface; like licensing. Though the HTML5 Host interface seems to have more features that the vCenter 6.5 HTML5 interface; like naming your vSwitches. I have not installed 6.7 because of all the products that do not support it yet, but I will in 3-4 months.