When should changes take effect

Another question about Info/Inspector windows on OS X: when should changes take effect?

Some info windows (like NetNewsWire’s) have an OK or Apply button. Others update the object as you make changes in the Info window.

I think having a button is somewhat old-school: it’s very much like the days when non-document windows tended to be modal. You’d click OK to make the changes or Cancel to not make the changes.

But yet a button in a modeless window gives the user the chance to be explicit about making the changes. You can back out halfway through, and just not click the OK or Apply button.

Such a button becomes a problem, though, if you have multiple panes of info. To what does the button apply? All the panes where you made changes, or just the current pane?

(In case it’s not obvious, I’m adding some per-feed prefs—such as for feed validation—to NetNewsWire, and I’m looking at prior art in thinking about how to add extra info to the Info window. And I’m finding that prior art is a jumble: there is no clear consensus as there is with preferences windows. Ideas are of course welcome.)