Mac OS X 10.7 is going to introduce saved-states with applications. This means, that your applications will essentially never “turn off.” In fact, they even removed the little dot of light under the applications. As a person who likes to keep applications off and only turn them on while I’m using them (i.e. I close Safari and other applications when I’m working—or at least, I often try to), I don’t know how I’m going to feel about having every application “always there.”
At least people won’t be confused anymore about the “state” of an application. I know many people who forget that applications are running, and the applications just compound until the computer grinds to a halt. It’s also hard to explain to first-time users, the concept of “hide” (especially to those coming over from the Windows side).
It works well on the iPad and iPhone due to the nature of their use. I wonder how it will translate over to Mac OS X, and how it will effect the learning process for new users and the old habits of old users.