I upgraded to Mavericks on Wednesday. I noticed that the Spaces aren't linked they way they were in Mountain Lion. I found out that to link them, all I had to do was go to Mission Control in System Preferences and uncheck the box that said "Displays have separate Spaces". The problem is that after I did that, I was unable to have two fullscreen apps on each monitor without having the same issue that was in Mountain Lion, where the space on the other monitor becomes useless. Is there a way to have the spaces linked, while being able to have fullscreen apps running on both monitors in a pair of spaces?