Can I remap UP and DOWN arrow keys in Aperture?
So, using a little plist trickery, I've managed to re-assign those keys.

The steps I took are the following:


Aperture > Commands.. > Customize
Duplicate current command set and name it "MySet"
Export &amp; delete the current set
Open it with Property List Editor
Find and Delete: MoveSelectionUp and MoveSelectionDown entries
Save and exit
Import it via Aperture > Commands.. > Import
Select it via Aperture > Commands.. > Custom commands set


So now the UP &amp; DOWN arrow keys are free to assign whatever you like (in my case Increase &amp; Decrease rating feels like the way to go!)