One of most important indicators for software quality is habitability. This can be see this from 3 perspectives: Firstly, how habitable is the code for others to live comfortably (convenient and simple) with. Then of course, there is always the habitability of the UI from the users perspective. And lastly, there is the habitability of the application for those that must administrate it (it is a good citizen and easy to administrate in the environment it runs in).
Of course habitability is not easily appreciated in software (like buildings) until it is in an executable form and is actively used in all three of these perspectives. I also find it interesting that if the software is truly habitable, then the time spent by all three of these user types is minimal. Or, at least it is fairly transparent in that the software stays out of your way or does not distract you when you use or change it.
As I recall (though I can't find a specific quote right now), Christopher Alexander always emphasized that one one of the most important criteria for quality in an architecture, is that the building must support (if not enhance) the peoples daily activities as they flow through it.
I will try to explore habitability in software applications and their associated frameworks as well as delve into the three perspectives of habitability over the next few months.