I think Google has done some really nice interaction design on these
new features. They've added some very useful functionality that will
fundamentally change the way we use search. Where once search results
were generic and out of the users control—dependent on search
optimization and "Google Foo"—we now have the ability to take some
control of the results, turning Google into more of a personal
research tool, rather than just a search engine.
And, somewhat surprisingly, the UI design is quite elegant. Animated
transitions utilizing fades and transparency make it perfectly clear
what is happening. Temporal, in-line messages help you learn how the
new features work on the fly.