Comment 22 for bug 149764

With Hardy, the compiz seems to support the hack i used in Beryl. Here's a solution:

make a script with these two lines (i.e. ~/.compiz-dual.sh)

## start compiz
DISPLAY=:0.0 compiz --only-current-screen --replace &
sleep 3
DISPLAY=:0.1 compiz --only-current-screen --replace &

then in gnome-session-manager add a new program:
sh ~/.compiz-dual.sh

this hack just runs a simple script a log-in, if you use the defualt name it's hidden, the script restarts compiz as two seperate sessions along both heads: note the DISPLAY=#.# line. You might need to change the numbers, a quick way to test weather your screens are 0.1 and 0,0 is to run (from the terminal,):

DISPLAY=:#.# gedit

that'll open gedit on which ever screen the numbers relate to.