Truly great software is great for many reasons, and one of the most important is the user experience.

UX experts can describe the specific factors that make great software great. Speed, design, conformance to a platform’s UI guidelines: Those all matter. Ease of use, compared to ease of learning. A powerful first impression. The correct balance of extreme simplicity vs. depth of functionality. Graphic design. Typography. Colors. Originality. Convenience. Intuitiveness. Elegance. Responsiveness.

The list goes on and on.

Say you’ve got a requirement for a killer business application. If nobody likes it, people won’t use it, and the software will fail in the marketplace.

Sure, if you are building in-house software, the CEO can mandate its adoption. For a short time, anyway. We all know stories about software the CEO adopted and which, very shortly, became expensive shelfware.

The best software today must be immediately useful, delivering value to both the individual user and to the organization. No owner’s manual. No on-line help. No training. No months of rollout. Of course, the UI metaphor will depend on the runtime environment: lots of drop-down menus and overlapping windows for desktop software. Pages and hyperlinks for Web apps. Big buttons for mobile apps.

It’s all different, it’s all good—and it’s all really hard to get right. Even Apple, famed for its incredible attention to detail, has released its share of hard-to-use stinkers for both Mac and iOS, and the beautiful UI of the Windows 8 desktop doesn’t always extend below the surface.

What I’m saying is that attention to UX detail needs to be as important as attention to the use cases, the algorithms, the data security, the caching and buffering, the workflow, and all the other moving pieces of software.