Agreed on the light mode not being visible enough, going slightly blind here. Wish we could just change the default contrast and revert to how it was before?
Another issue is that the new icon that is attached on gameobjects to indicate there's a playmaker script attached is also not very visible anymore, I'm on an iMac retina, so all the white logo parts makes it blend with the background, personally I'd prefer the old red logo so you can instantly see the scripts.
And a third is that the scene no longer automatically shows from the start which gameobjects have a script attached. You have to find one blindly, while the Playmaker Editor is open and then everything will refresh and show the icon. :/