I agree that the interface is clean and the program looks good, but this is another GTD program I try that falls short of the GTD promise.
Where can I select the level of mental and physical energy for my tasks? And priorities? And "Waiting For" items related to tasks I delegate?
The only one that works for my needs is Thinking Rock, with OmniFocus being my second choice that I never use.
ThinkingRock probably has the ugliest interface, but its functionality is excellent when it comes to the GTD methodology.