I have tested with a macbook pro (Nvidia 9600 inside). I can setup a TwinView between my macbook screen and a 1600x1200 monitor. Unity works fine, but twinView takes some times to configure. It sometimes refuse to set a configuration that I know to be working...
I recommend trying again with the latest pre-release of Oneiric and report the findings.
I have tested with a macbook pro (Nvidia 9600 inside). I can setup a TwinView between my macbook screen and a 1600x1200 monitor. Unity works fine, but twinView takes some times to configure. It sometimes refuse to set a configuration that I know to be working...
I recommend trying again with the latest pre-release of Oneiric and report the findings.