(My pet peeve with Metacity is that if you have a screen with a low vertical resolution like you would find on a widescreen subnotebook, you can sometimes get into a situation where you are not allowed to move a window up off the top of the screeen so you can access buttons on the bottom of said window. It's a real usability problem for anyone with a subnotebook, or just a small screen in general.)
I see I am not the only one bothered by that too. Changing screen resolution has become much easier now that we have xrandr than it used to be. Windows created bigger than the screen can handle has come up quite a few times for me in the past year. You would think the window manager would be smart enough to know that a 800 vertical pixel window will be useless on a 768 pixel desktop. Any buttons at the bottom will not be unusable without trying to manually shrink the window by clicking on the top of the window, dragging it down, releasing, moving the window up some, and repeating if it still doesnt fit. I think any window that is created should be autoreduced to the max display resolution(minus non hiding panels too) if the X or Y is bigger than the desktop. It sure sounds good anyway.
