I have a 27" iMac with 2TB and 8GB of ram, and I have photos changing every five seconds as my desktop background. It worked perfectly fine and transitioned wonderfully on the other osx but now this lags considerably and strains my eyes with the quick transitions. Every time I switch a space the desktop picture freezes for 10 seconds before adjuting. Anyone else having this problem? Also, I'm noticing everything is running much slower and freezing a lot more often. Before I could watch a movie and work in photoshop at the same time but now it freezes every now and then.