Change the mouse-over text of filters to make more explicit
I have been using GTDNext for over a week and I still get confused about what clicking the filters (e.g. "Filter Active Items", "Items with due dates", "Filter Focused items", "Hide complete"), button actually do!
The problem with the word "Filter" is that it can mean filter in or filter out!
Also the mouse over text needs to change depending on whether the button has been greyed out.
I suggest something like
"Show just Active items" (or "Remove 'just Active items' filter")
"Show just items with Due dates" (or "Remove 'just Due dates' filter")
"Show just focused items" (or "Remove 'just focused' filter")
"Show Completed items" (or "Hide Completed items"