Finally upgraded my 2011 MB Air (10.7.5), 4GB memory to Mavericks. Upgrade went very smoothly and took about 2 hours to download, install, and optimize. Only one app was incompatible so that's not bad. The oddity is that when I press the Power button to shutdown, I have to hold it in for about 6 seconds before the dialog box appears. Under 10.7.5, just touching the power button resulted in the dialog box appearing. Also, the response of the dock seems to be slow. Once the dock has been activated once, the response is fast. My imagination or what?