the first two or three version were unbearably slow and awkward, but since the 'card' redesign, it's reactive (coming from a fps fetishist on a 2006 laptop) and usable. When G+ came, FB had all this in place, their html framework was hyper lean in all possible ways. Every time I had to use FB after G+ I was shocked to witness the difference. FB gained some weight since but it's still a smooth cut.