Comment 104 for bug 771788

I did it!!! finally!!!!!
As I was saying before. the graphic driver is not being used. When you see unity it's because you are using nouveau. Then you try to install the binary drivers, nouveau gets automatically removed, AND you can't start unity any more unless you activate the experimental 3D support (actually I'm not sure, I didn't try to run unity again with the open source drivers)

Solution:
Download the official drivers from nvidia.
We are NOT going to use the "Additional Drivers" tool nor apt to install the drivers. we are going to use the ".run" file from the nvidia site.

Edit /etc/default/grub (sudo gedit /etc/default/grub) change GRUB_CMDLINE_LINUX_DEFAULT=... to GRUB_CMDLINE_LINUX_DEFAULT="nomodeset" and do the same with GRUB_CMDLINE_LINUX

Example:
GRUB_CMDLINE_LINUX_DEFAULT="nomodeset"
GRUB_CMDLINE_LINUX="nomodeset"
#GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
#GRUB_CMDLINE_LINUX=""

save the changes and run:
sudo update-grub

Reboot your system. the following line is not needed but this way you will make sure nouveau is not running at all:
sudo modprobe -r nouveau

Now cd into the folder where you downloaded the file, chmod and run it as root
Example:
chmod 750 NVIDIA-Linux-x86_64-270.41.19.run
sudo ./NVIDIA-Linux-x86_64-270.41.19.run

Now say yes to everything, reboot the system, and you are ready to go!
Good luck!