Hi. Installed the Yosemite beta on a 2013 Macbook Air: In short - I am screwed. Almost all actions result in a beachball for 15-20 seconds. Deleting a file in finder, browsing the system preferences, opening a webpage etc. There seems to be a big problem going on in the system that affects almost all UI/GUI actions/whatever causes it. I also notice that when the machine boots, it takes a long time to get the Airplay, Wi-Fi, Bluetooth and battery icons up in the toolbar. I tried re-installing the whole OS, same thing happens. I also deleted all sorts of 3rd party software that might could cause this, but still no luck. Any ideas?