OK, so mabe the pun is not funny, but if you can do everything else and also make the site engaging, then you certainly should be well paid for your efforts. Much of today's software is dry and boring, and if you could make an interface that entices the user to stay around and explore your site more then you will likely benefit from increased sales or whatever your site is attempting to accomplish.

It sounds like the concept of Engagement might be counter to the concept of an "Invisible Interface?" That is, how do you make something engaging while keeping the user focused on the content? Well, a simple example might be a page of related links. For another example, if you have a used car web site, you might be able to use "recommender" technology (which we use here at Bellcore, for some similar tasks) to add a few links to every used car page that "recommends" other used cars that are similar. This might lead a user that finds one car, but then based on your recommendation looks at another car they might not have previously considered. Maybe its not as engaging as a VRML interface of an used car lot, but at the simplest level it would accomplish the goal of keeping your visitor interested in your site which is a good thing.