In Steve Job’s keynote yesterday there was a mention of Jim Allchin’s desire to buy a Mac. Today the context in which Allchin made that statement has been revealed. In his email Allchin keeps reiterating “scenario, simple, fast’. Any software developer should take these words to heart. The order of these three words is also significant. The most important thing for any software is it’s usage scenario.Usage scenario help in making the right tradeoffs while designing software. But for the few lucky people who write device drivers and are constrained by the operating system interface on one end and the device interface on the other, all other software developer need to pay a lot of attention to the design of the interface that their software presents. As far as the user is concerned the interface is the software. She does not care how extensible, modular the software is. Nor is she bothered if it uses the latest technology or is Web 2.0 compliant ;-). All the users want is to achieve their goals with the minimum effort.