My only concern is the potential for clutter. As others have pointed out, facebook tried this, and it made for completely unnavigatable user pages. I don't expect that to be quite the case here, but I do note that the updated pages tend to be larger than they were before. It's an issue for people with slower internet connections.
I do think the new layout is very sleek looking, however, and I like the ability to customize what is on it. I just fear the coming onslaught of Too-Many-Boxes.