There's a bit of that, but for me the key would be e-mail. It's a thoroughly "text-y" application, but not being able to handle inline pictures would be a problem for me at this point.

The "operating system in disguise" idea is an increasingly minority view these days, primarily because Emacs is single-threaded. It does a lot of things, but the ones that aren't text-oriented are generally implemented by calling out to an external program -- in a separate task if appropriate.