In bug 358674 Thomas Thurman suggested anyone who wants unidirectional maximization by middle or right clicking on the maximize button should advocate it in a new bug, so I'm doing that now.

Some positive arguments in favour of a multifunction maximize widget:

It's a Unix norm. Off hand I can't think of any other X wm that doesn't have this feature. GNOME shouldn't be a poor man's Windows (or even Mac OS) clone. Why discriminate against users who are used to other X wms?

The maximize button is more closely associated with maximizing than the title bar in general. Binding specialised maximize actions to a button widget that's known for maximizing makes more sense to me than adding them to a list of general actions that can be bound to doing something "weird" with the title bar.

In answer to some arguments the developers used against a multifunctional maximize widget in bug 358674:

Havoc Pennington thinks having different mouse buttons do different things on a button widget is "insane". I disagree. Having only one action per widget is counter-productive for power users. Mac OS has always had to use keyboard modifiers to compensate for only having one mouse button (and I'm pretty sure most Mac users buy PC mice since Apple started using USB). Surely using a spare mouse button is more productive and easier because it only takes one hand. Acorn's RISC OS, which was acknowledged to have one of the best GUIs ever, used the convention throughout that right-clicking would perform a similar action to left-clicking but with some sort of modification (eg left-click on OK would apply and close a dialog box, right-click was apply and keep the dialog open); middle click was reserved for menu.

Anyway, the current behaviour *is* that the button widgets do different things if you click on them with different mouse buttons. Not only that, but they effectively stop being distinctive controls and turn into a blank bit of title bar. How is that better?

The developers say the chosen method fits in better with the ability metacity already had to bind different actions to double-click and right-click on the title bar. But they regard this ability as an aberration anyway so why use it to justify doing something in a way differently from what users are more likely to be used to?

They say that a multifunctional maximize button is "undiscoverable". So what? Metacity already has plenty of other "undiscoverable" features. And the chosen solution is even more undiscoverable because if you want both directions to be available you have to rebind right-click (or middle-click, but no way would I want to lose the lower action) as well as double-click, and this is a hidden gconf setting.