I believe performance does matter and should factor into the design of a system. There is an ISO guidelines on software system requirements and specifications t

I believe performance does matter and should factor into the design of a system. There is an ISO guidelines on software system requirements and specifications that has a section for performance requirements. It does matter even for banal, non-critical or non-life-threatening software systems. Another often-overlooked requirement: environment. Does the human using your software system have to pay attention to more important situations around them? Is the environment they're using your software in noisy, stressful, dangerous or dirty? Should you expect frequent wireless interference or degraded wireless performance? Reading the ISO specs are pretty boring, so is the SWEBOK guide, but it's rather interesting to think about software in terms of the whole system and not as an artifact unto itself.