Font smoothing is wrong after Mavericks update on MacBook Pro with high-res display (not retina)
The system font was changed to a modified version of Lucida Grande. It was mentioned in the What's New in Cocoa presentation:



The normal Lucida Grande doesn't seem to have changed:



There is still this hidden preference for using a lighter text rendering style:

defaults write -g AppleFontSmoothing -int 1


Quit and reopen applications or log out and back in to apply the changes.





The regular faces of the new and old versions don't look that different, but the bold face seems to be bolder in the new version.

The screenshots posted by gooogalizer have bigger differences though, so maybe the new version is rendered in a different way on high-resolution displays, or maybe something else changed in the way text is rendered on high-resolution displays.