I noticed that my 10.9 installation uses less space than my 10.8 installation with disabled "hybernation" file: As I use a 60Gb SSD I discovered that I could liberate like an extra 7gb of my 10.8 installation a few months ago, and so I did. Now I noticed that my 10.9 installation has a couple extra Gb's free, WITHOUT THE NEED TO DISABLE WRITING THAT HIBERNATION FILE... Interesting... Now I wonder how apple managed to do this, and if my laptop is asleep and battery runs out, what would happen... It's a great idea for laptops with ssd's i think. Maybe the new system waits until battery is nearly death to write that "hibernation" file... Perhaps any expert could confirm how they did it? thanks a lot!!