Good software does what you want. Preferably without your having to tell it to. And it matches your mental model of what you expect things to work like.
We have come a long way since the days personal computers were severely constrained in their resources, but some traditions have not changed. The humanized weblog looks at the save icon, but I want to point out that the “saving” “feature” is itself an anachronism. There is no analogue of the concept of “saving” a file in the real world; when you write on a sheet of paper the change is permanent. Why, then, does most software require you to explicitly “save” something if you want to leave it permanent? The answer, I guess, is that a long time ago, a “save” was an expensive action (I remember seeing “Saving…” progress bars), so you wanted users to be in control of when it happened, so as to not annoy them.
Today, personal computers have enough resources that in many applications (such as text editing), there is really no reason for software to insist that you remember to “save”, so as to not lose your work. Still, programs continue behaving this way, partly out of tradition, and partly because no one gives a thought to usability.
Fortunately, the rise of applications on the web brought with it an “everything old is new again” phenomenon and programmers began to take a fresh (and naive) look at everything, which, while often causing them to stupidly repeat the mistakes of desktop programs from decades ago and generally be inconsistent, has also allowed them to throw away meaningless traditions in situations where they don’t matter.
I believe it was Gmail which started this, and now Gmail, Blogger, WordPress, Google Docs, and any number of online text editing applications now “automatically save” your work for you every few seconds, and this idea is finally (slowly) taking hold in desktop applications as well.