[One of a series regarding Snow Leopard’s new Finder menu commands.]
Press Option, and the File menu’s Open command changes to Open and Close Window (with the expected change of Command-O changing to Command-Option-O). This doesn’t sound like a useful command, does it? After all, opening and then closing the window automatically doesn’t give you much time to do anything, even if you’re a super-speedy reader. It is useful however, because its full name is “Open a new window for the selected folder, and close the one the folder is in.”
Now, if you think about it, that’s not all that useful, either, is it? If you double-click on a folder in any but Column view, its contents take over the window anyway, so why would you need to close the “parent” window when it just disappears?
Aha! That’s the problem with just “thinking about it” instead of trying it out! When you open a folder in the current window, it takes over the window, using that window’s settings for view, icon size, sorting, and so on. If you open it in a new window—which is what happens with the Open and Close Window command—it displays any settings you assigned to the it last time you opened the folder. Now, that can be handy.
(But it can be quicker to just Option-double-click on a folder to open it into a new folder while closing the parent window.)