EDIT o post acima:
Consegui resolver o problema, mas não para 3D porque o Compiz falha. aqui está o novo xorg.conf:
# nvidia-settings: X configuration file generated by nvidia-settings
# nvidia-settings: version 295.33 (buildd@zirconium) Fri Mar 30 13:43:34 UTC 2012
Section "ServerLayout"
Identifier "Layout0"
Screen 0 "Screen0" 0 0
Screen 1 "Screen1" RightOf "Screen0"
InputDevice "Keyboard0" "CoreKeyboard"
InputDevice "Mouse0" "CorePointer"
Option "Xinerama" "1"
EndSection
Section "Files"
EndSection
Section "InputDevice"
# generated from default
Identifier "Mouse0"
Driver "mouse"
Option "Protocol" "auto"
Option "Device" "/dev/psaux"
Option "Emulate3Buttons" "no"
Option "ZAxisMapping" "4 5"
EndSection
Section "InputDevice"
# generated from default
Identifier "Keyboard0"
Driver "kbd"
EndSection
Section "Monitor"
# HorizSync source: edid, VertRefresh source: edid
Identifier "Monitor1"
VendorName "Unknown"
ModelName "DELL P2311H"
HorizSync 30.0 - 83.0
VertRefresh 56.0 - 76.0
Option "DPMS"
EndSection
Section "Monitor"
# HorizSync source: edid, VertRefresh source: edid
Identifier "Monitor0"
VendorName "Unknown"
ModelName "DELL P2311H"
HorizSync 30.0 - 83.0
VertRefresh 56.0 - 76.0
Option "DPMS"
EndSection
Section "Device"
Identifier "Device1"
Driver "nvidia"
VendorName "NVIDIA Corporation"
BoardName "GeForce 8500 GT"
BusID "PCI:1:0:0"
Screen 1
EndSection
Section "Device"
Identifier "Device0"
Driver "nvidia"
VendorName "NVIDIA Corporation"
BoardName "GeForce 8500 GT"
BusID "PCI:1:0:0"
Screen 0
EndSection
Section "Screen"
Identifier "Screen1"
Device "Device1"
Monitor "Monitor1"
DefaultDepth 24
Option "TwinView" "0"
Option "metamodes" "DFP: nvidia-auto-select +0+0"
Option "Rotate" "left"
SubSection "Display"
Depth 24
EndSubSection
EndSection
Section "Screen"
Identifier "Screen0"
Device "Device0"
Monitor "Monitor0"
DefaultDepth 24
Option "TwinView" "0"
Option "TwinViewXineramaInfoOrder" "CRT-1"
Option "metamodes" "CRT: nvidia-auto-select +0+0"
Option "Rotate" "left"
SubSection "Display"
Depth 24
EndSubSection
EndSection
Section "Extensions"
Option "Composite" "Disable"
EndSection
Eu o criei usando configurações nvidia, não com visão dupla, mas com telas X separadas, a tela 1 é absoluta e a tela 2 é à direita de. Eu verifiquei o Xinerama ativado. Então eu editei o arquivo xorg.conf para adicionar a opção de rotação de ambas as telas (veja o arquivo). Funcionou!