Picking up where we left off in Part 1, this video tackles the concepts of Feedback, Recovery from Errors, Simplicity and Goal Oriented.

In a nutshell...

#5 Feedback

Feedback is acknowledging users actions and letting them know when the program is busy.

Research finds Feedback the #1 influence on user satisfaction

Feedback Deadlines:

Button clicks must be acknowledged within 0.1 seconds
Moving and Resizing can't lag behind cursor for more than 0.1 seconds
Busy Indicator: Any system delay over 1 second must display hourglass cursor
Progress Bar: Any system delay longer than 3 should display a progress bar

The ability to reverse mistakes, and recover crashed data.

Ctrl+Z: Works pretty well in Blender, although it's mode specific resulting in sometimes reversing data made in a different mode.

Crash Recovery: Although it exists, could be implemented better with a dialogue on reopening.

Can be broken down into 4 sub-categories:

Hierarchy: Arranging functions so most used functions are most visible.
Structure: Principles of Proximity and Similarity- Separating unrelated functions, make relatable functions look similar.
Design: Clear representation of what's on screen, with larger text and more contrasting wireframes.
Vocabulary: Avoiding Jargon wherever possible. Making tooltips simpler, and in plain english.

Software must be designed with the users goals and intentions in mind.

Studies find that users pay very little attention to software functionality that does not lead them to their goal.

All users must cross what cognitive psychologists call the "gulf of execution" to achieve their goal.

By better adhering to all the principles of:

We can make Blender easier to use for not just beginner's but experienced users too.

In two weeks I'll be posting my Full Interface Proposal for how to tackle these issues. Stay tuned!