Desktop is late 2012 iMac 21.5, 3.1 GHz i7, 16 GB RAM, FusionDrive. Fast machine, runs Mavericks speedy fast. I installed the public beta onto a formatted bootable Lexar 64 GB USB3 drive. It installed just fine and runs, but it's extremely slow. It is slow to load apps (takes minutes not seconds). Once loaded the apps are OK (such as browsing in safari, etc.) but loading them initially is super slow. I made sure the spotlight indexer is not running. And I also did the "Repair Disk permissions" on the drive, which actually helped a tiny bit. Do you guys have any other tips or ideas for me to try to get this running fast? I did a fresh install, I did not import anything from my main mac account, I haven't even enabled iCloud or iMessaging or anything like that yet. I already submitted Feedback to Apple regarding the issue.