I think this article has some interesting points about tailoring things to your audience, and thinking about who your audience is.

Specifically for Hotmail, I prefer the newer Windows Mail (or whatever they call it this week) version to the old Hotmail, but my mother was completely unable to use the new version.

I guess this is the danger when trying to create a product that is all things to all people... Microsoft's solution seems to be to have two products and pretend they are just one.