Nancy, usability studies are really the way to go, and even better, if you can film the usability study for later review. It's really key to see the non-verbal responses when users attempt to complete a task. The way that they may hesitate, start to press the wrong button, or seem flustered.
William, you're right, Engineers are not normal people and Software Engineers, even less so (judging myself and close friends). The first test I always perform is to have my wife attempt to navigate the interface. She will always use the interface in a way that surprised me. When possible, I like to have the user capable of achieving the same task in multiple ways so that everything they do is right, instead of everything they do being wrong. After all frustration is defined as "blockage to a goal".
Sometimes I would be happy to go back to the days when I didn't know the phone number of the person calling (Caller's ID), or had to reachable 24/7 (cell phone, email on my cell phone, text on my cell phone, etc.). I can hear the boos, lol. Cell phones like the many other products and systems with user interfaces (UI), can have you saying "who in the world design this thing????". Sometimes I don't think the design companies actually have design requirements or even take the consumers into consideration. Some UIs I have found to be easy while others haven't been the opposite. Just when you have your cell phone all figured out it is time for a new one and I have yet to have a new phone that allows me to navigate the same way as the last one.
I believe designing a user interface has to be extremely hard... guess you can't please everyone.
I have to agree with the folks that usability studies are definitely essential in today's day of products laden with software code. Trying to get fancy or creative for the sake of being creative isn't going to resonate with users who are looking to do things quickly and who are often doing whatever they're doing on a cell/smart phone while they're doing something else. If you have to work it too much, it's just low utility.
For industrial control applications, or even a simple assembly line, that machine can go almost 24/7 without a break. But what happens when the task is a little more complex? That’s where the “smart” machine would come in. The smart machine is one that has some simple (or complex in some cases) processing capability to be able to adapt to changing conditions. Such machines are suited for a host of applications, including automotive, aerospace, defense, medical, computers and electronics, telecommunications, consumer goods, and so on. This discussion will examine what’s possible with smart machines, and what tradeoffs need to be made to implement such a solution.