Almost all the sites I'll develop take advantage of progressively enhanced components or at minimum, widgets that are bootstrapped server side. Angular wants you to load everything via AJAX - that can get heavy very quickly.
This is also evident within the codebase. You find yourself dancing around DRY violations as you pass models to your markup rendered server side and also serve the same/similar content to Angular via JSON.
Now this aside, Angular wouldn't require much work to let it play an enhancement or migration role. You can already see Google have implement their own 'private' method on the homepage of Angular.
Another problem that grates me about Angular is dynamic routing and loading additional Javascript on the fly. I was recently building a portlet based site. The intention was to make each module entirely configurable by other developers - that meant passing control to their controllers and allow them to enhance routing. As it stands you have to do it declaratively or using some nasty hacks.