My experience has been that users want to pave the cow path. They want you to take a process they are used to doing on paper and just make it electronic. My least favorite phrase in response to some edge condition is, “don’t worry about it, it doesn’t occur too often.” Then I have to explain to them that if it occurs even once, I have to deal with it. The other problem is that they will ask for what they think you can do (at that moment). Once they see you do that, then they want you to add to it. I generally ask them to give me their wildest fantasy on what they want to accomplish and then we will scale it back to reality. In other words, don’t tell me you want a wet bar on the other side of the room after I’ve laid the concrete slab.

To address your concept of simplicity, I agree. I don’t want buttons on the screen or being enabled until it is appropriate. Too many times I’ve seen screens that allow entry of data that is not appropriate at the time and then the program allows them to add bad data to the database. And guess who gets to clean it up?

The user must be constrained, but still given the sense of freedom, not that of a strait jacket that must be worn willingly.