Now, we've all heard the argument, "our customers don't use computers often, so we need to keep things extremely simple." We've also had people argue the opposite of that: "these are smart people with a great deal of computing expertise and we need to put the power at their fingertips."
Both of these arguments attempt to use general computing/technology expertise as a way to direct the design of a particular application experience. Now, if we relied on such arguments, we'd almost certainly have poor results.
It is useful to make sure we appreciate this subtlety. This leads to another set of ideas:
In the end, we should still treat all people as reasonably smart and quite adaptable. In this way, I'd treat everybody the same knowing that they are going arrive at their own version of success within my application based on how well I design to good usability principles.