Think about it. You're putting in this cool new feature, it's going to save the users a lot of time, give them a ton of functionality and, hence, save them a truckload of money. AWESOME!
So, first we nail down the functionality... right? WRONG!!!
First you figure out how the users will exercise the new functionality, because that's what you're ultimately giving them- a new user experience. a new interaction mode.
Unless you make sure the user is going to find the new interaction intuitive, any new functionality, however efficient, is a burden. If you make the user jump through a lot of hoops just to do his everyday job, your new feature SUCKS
I actually experienced this first hand recently. We enhanced the TIL Regulation dashboard in an LOS to allow the users to monitor loans as they get dangerously close to the limits and notify them once they fall over. I actually reordered all the controls on the screen just to keep logically related data together. The new design was so intuitive that the Business Analyst approved it in a heartbeat and sent out an appreciation note! (Pat myself on the back)
At the same time, another team member was working on the screen used to configure the regulation limits. Man did they miss the bus! They wrote up the whole screen, new popups et al, and then sat around thinking, 'What if the user checks this but doesn't fill in that...?' WHOA!
When he asked me for an opinion, I said that the new validations he was thinking of were cool, but, '...wouldn't it have been much more logical to have thought about this BEFORE
you built the whole thing?' Nevertheless, he ended up putting in the validations (in this screen and a few others!). Rework can be such a productivity killer!
The user always comes first. Kathy Sierra agrees in her blog post captioned Ignore the competition