Well, maximizing a window with three Xinerama screens will let that window become maximized in its current "screen".
What would happen with that Matrox Tripplehead 2 go?
Would that window be maximized over two monitors?
(for example if you press maximize on Firefox, it would be bad if that browser window allays tends to be maxed across two screens....)
Edit: Just found this thread: http://www.nvnews.net/vbulletin/showthread.php?t=126134
So nevermind, thanks