The best user interface is the one that no one notices. It should just melt away in it’s function. It should get out of the way rather than pose as a hurdle to cross to achieve something. Reducing the number of clicks for each operation is a good start. Making the response time really fast (sub 100ms) also helps. But these are just tricks. What really matters is the overall concept. The concept of what needs to be shown and what can be hidden. What is really necessary for the user?. What can be defaulted or figured out in some other smart way? Visibility is key. Whatever is shown on the screen should be easily understood and discernible. Unlike the new Google icons. Colors convey a mood. A combination of colours and movement can convey an emotion.