Devil's just trolling, as he does.

Everything has been done before, but every dog has his day. There are countless technologies that come around and fail, only to be reinvented years later to wild success and fanfare. The N900 may be the fusion of several different cases of that, or it may just be a niche device that serves a certain small population of users very well. It's too soon to tell.

Certainly you're not going to find a "killer app" unique to Maemo in the traditional sense, because (as someone already pointed out) anything great in software has probably already been done everywhere possible (and is coming soon if it hasn't). What people are more likely to find with the N900 is the "killer toolbox" that has all the components of a solution they happen to need. That's its real strength--the breadth of components it has available to it--and it comes from Maemo's linux origins, where the paradigm is single-purpose but solid tools and easy ways to chain them together to do fantastic things.

Those who will get the most out of the N900 are those who are able to visualize their own personal killer app, and then make (or get others to make) it a reality. And wouldn't you know it but we've got this awesome community doing just that, every day!