Even though I like somewhat denser interfaces, I know that lots of whitespace is GREAT for new users. Just like I know everything needs to be in the UI (~80-90% of users click the undo button instead of typing Ctrl+Z in many apps). There has to be space for a learning curve for any interface.
The ability to make things denser is important, but high density is usually only relevant for power users. It should not be the benchmark by which a UI is judged.
EDIT: Actual ctrl+z statistic is inaccurate. Details included in a further comment.