UPDATE: Since this question has got many views, I just want to add that from Ubuntu 13.04 onwards, proprietary drivers installed perfectly on my MacBook. Versions of Ubuntu prior to 13.04 will have problems

I recently upgraded to 12.10 and was just checking for proprietary drivers to be installed. I found this in software sources

When I enabled Nvidia binary Xorg driver, unity disappears along with the launcher and everything. I just have the wallpaper. I did manage to open the terminal and open software sources and select the nouveau display driver which fixed it.

Question is how to enable NVIDIA binary Xorg driver and have everything working?

Hardware: Apple MacBook Pro 9,1 Mid 2012 15 inch non-retina. NVIDIA GeForce GT650M

EDIT: I tried the solution here. And now, when I boot into Ubuntu, I get a blinking cursor. That's all! No tty1, nothing. help !!

EDIT 2: I inserted the Live USB and re installed Ubuntu without formatting the partition. At least, I didn't lose my files, but all softwares are gone. And the output of

lspci -vnn | grep '''[030[02]]'

01:00.0 VGA compatible controller [0300]: NVIDIA Corporation Device [10de:0fd5] (rev a1) (prog-if 00 [VGA controller])

EDIT 3: So, I was checking the link which Shrinivas gave, namely this one http://www.dedoimedo.com/computers/ubuntu-quetzal-nvidia.html and it doesn't work for me. Specifically, where he says to run the command modprobe nvidia_current, I get the output

FATAL: Error inserting nvidia_current (/lib/modules/3.5.0-22-generic/updates/dkms/nvidia_current.ko): Operation not permitted

So, what's the problem? To reiterate, I'm using Ubuntu on an Apple MacBook Pro Mid 2012 15 inch non retina 8GB RAM with NVIDIA GeForce GT650M