A new hint was posted today on Mac OS X Hints explaining how to re-gain use of the arrow keys in Quick Look’s full screen mode. The solution worked but I thought that there had to be a better, quicker, easier way.
So, I started trying various other keys when in Quick Look full screen and I stumbled upon a much easier solution:
1) Get into Quick Look full-screen using command+option+Y
2) Hold command and tap “`” — the button next to 1 (this is the command to ‘cycle through open windows’)
3) If you only have the one Finder window open, just keep command down and tap “`” again to return to the original window
4) If you have multiple Finder windows open, either keep tapping “`” until you return to the original window, or just add “shift” when clicking “`” to ‘cycle through open windows in reverse’ (command+shift+`)
5) You can now use the arrow keys to browse through your files in Quick Look full screen mode
Note: Clicking “esc” to quit still doesn’t work, but you can use command+option+Y again to close Quick Look
HD Video Demonstration: