Software Should be Simple
The interface to software should be clear, without surprises. Engineers working on the project should not be deciphering code. Documentation is implied as part of the system, enabling all users to understand the software package better.
Software should handle changes smoothly. Great software feels like it was designed for future changes. The documentation will instruct an engineer's strategy, removing ambiguity of how something works.
Load spikes, accidental misuse, and business growth should not bring software crashing to the ground. Systems should be designed to handle faults gracefully. If there are errors, they should be reported clearly.
Leveraged by Other Systems
When software simply does its job, and does it well, it will be an asset to other systems. When software becomes convoluted, it will hinder other systems.