Using E17 from the RPM repository, CentOS 6
3 monitors:
- Onboard ATI, open source drivers, VGA out (Screen 1)
- PCIE NVidia, proprietary drivers, VGA + HDMI out (Screens 2 & 3)
When enabling composite mode, all 3 screens mirror the first desktop; the mouse can move to desktops 2 and 3, but can't seem to interact with them (maybe it is interacting, but those desktops aren't visible since they're all showing desktop #1's content)
Then when unloading the composite module, all desktops lock up completely, though the setting "composite disabled" is saved successfully.
Rebooting with composite module disabled, it seems to work fine.
(Other hardware-accelerated compositors have different horrible problems with this setup, I'm hoping E17's software one might do better, though I can't find the hardware / software renderer toggle, so maybe it's defaulted to hardware mode and this is a hardware problem?)