
Are you on iPhoto 11? As on older versions IIRC that was possible, if set up correctly. Besides the slideshow part.If iPhoot does that - WITHOUT ANY FUCKING FINGER DANCE OF ALT/COMMAND/F/ or whatever, then please show me.
iPhoto - Preferences - General:
- Double click Photo: Edits Photo
- Edit Photo: Using full screen

So with double-click or return: go into event -> go fullscreen & back into event & back into events. Works fine here with just arrow keys and Return or doubleclick.