One one hand your users are the stakeholders in your application. If they find it too hard to use your application, they wont, or they'll make life difficult. The end game in this scenario is generally lost time due to extra time spent working with the minority.

OTOH, it is impossible to please everyone, and using the latest "reasonable" technology often means your project will come to fruition quicker, and be more maintainable due to the absence of "legacy" code.

OTOH programming at the lowest common demoninator will cover everyone, but may not be as sexy as it could be.

In my experience, the people who scream teh loudest are the people who are in their own little rut and dont want to change. In these cases I personally (as the developer) coach them thru' the "difficult times". It makes them happier, and the devel/support team happier.

I'm generally of the opinion of surveying the users of your system, being careful to get a broad cross section, and get each department to sign off the design. In cases where a consensus cant be reached, careful thought is given to the design, which is then documented (outlining the reasons "why not") then mandated to the users via management. I have to say I'm lucky enuff to have strong management to support decisions reached...

Two words(tm): careful planning.