2.       Balance between simplicity and complexity for universal appeal.  You can expect to cater to beginners and advanced users at the same time.  Make sure your product emphasizes easy and intuitive use for common tasks.  You can then offer more advanced tasks for advanced users that are hidden from view but are available to those who have the need or motivation to seek them out.

3.       Flexibility that covers all possible scenarios is always a major faux pas.  I have worked with designers that want the product to handle all situations that may arise – regardless of what makes sense.  The simplest example of this is providing features for create, read, update, and delete for data.  If the data that we are considering is historical data, does it really make sense to allow customers to edit it?  Some things just don’t make sense and should not be considered as features for the product.  Period.

4.       Visibility affects understanding and trust.  I designed an accounting product that was used by finance specialists around the world.  The accountants were very concerned about automatic calculations for currency exchange rates as well as others.  They required transparency into these hidden features before they felt comfortable with the system.  Every software product has a different customer target market and hidden features.  It is up to the designer to dial in the appropriate level of visibility into those hidden features so that customers feel safe and comfortable with the product.

5.       Evaluating a product based on number of features is overrated; it’s inventing a new need that counts.  Adding features may appear to improve the attractiveness of a product, but ultimately it decreases the customer’s satisfaction.  The key ingredient for a successful software product is inventing something new that makes the customers life easier or more satisfactory in some way.