I've just been playing with beta 4. Looks pretty nice, I like the fill light control in develop, don't like the scrolly bits at the bottom of the panels though...
Anyway, I tried the lights out mode but it leaves a thin white border around the image which seems a bit odd given the whole point of lights out is to remove the artificial whites in titles etc. There was no lights out mode in beta 3 for windows so I'm not sure if the border is new. Was this border in beta 3 on the mac?
Justin.