I wrote a patch which adds a new gconf-editor entry which lets the user switch the new window placement behaviour of metacity. The patch can be found here: http://matthiasjansen.de/~maz/gentoo/metacity-2-xinerama-place.patch (also attached) Also a patch for the metacity ebuild to include the patch in the files dir.
Created attachment 93496 [details, diff] patch for metacity to let the user switch the new window placement behaviour
Created attachment 93497 [details, diff] Patch for the metacity ebuild to include the placement patch
This patch should go upstream and won't be accepted in Gentoo unless it is accepted there. So please, file a bug at bugs.gnome.org and leave the bugnumber in this bug. Thank you.