Re: Poor Xinerama Performance
This is likely more due to Xinerama than the nvidia driver. Does the performance improve (with just two displays) if you switch to TwinView instead?
If you'd like to have this investigated further, please generate and attach an nvidia-bug-report.log, along with specific details on how to replicate the performance problems you're reporting. It would be especially helpful if you could provide some kind of benchmark so that we're comparing apples to apples.