I remember for all the big Facebook updates the backlash was intense, but now most embrace those changes as an improvement (700 million users testifies to that). Google's changes seem to be embraced by many, I don't sense the extreme backlash. I for one love the changes.
Google's UI upgrades have me really excited. What I really like about Google and all their products is how utilitarian they are. Their products are not about looking pretty, but about giving me the most useful features I need. What I like about the new UI look is that they are thinking about the aesthetics of design more. Gmail used to look like a bland data grid from excel, and it was very dense with information. Now there are more pixels in between rows and columns in the new Gmail, giving the layout visual space. The color changes also make the UI more interesting to look at and quicker to navigate. But the best part is the dark navigation bar at the top. Love that.