Is there a way to get OSX style file previews in the file browser?

There is a program that I think do the thing you asked for (not 100% sure since I never used OSX), it's called sushi. It basically open a windows giving you preview of all files and directories pressing the spacebar.
It is in the default repository so to install use can type in a terminal

sudo apt-get install gnome-sushi

and you have to restart nautilus: type in the terminal

nautilus -q

to close it and click on the home folder icon on the dash to start it again.