HannibalKing;148816
It takes up about 6.4gb.

It´s not that much as I believe it could take… but anyway I will delete some demos and other stuff to be sure I have the space enough.
Thanks Hannibalking

I have played it both installed and uninstalled. I did my first playthrough uninstalled and I found it much better installed. Like several people have said it reduces load times (not by much on mine…reduced a 4th of a second) but made it so the disc didn't have to spin so often which made it run quieter and allowed it to handle some of the more intense screen filled moments better.