I have a 13" mid-2012 MBA with factory-installed OSX with all updates applied, running 10.8.4
I too was experiencing the problem where the MBA would not reconnect to my home WiFi network after sleep. But through careful observation I noticed that the problem not only occurred when waking from sleep but also when I turned off the WiFi network and then turned it back on. In this latter case, when I turned on the WiFi network it would not find my preferred home network. I would have to wait a few seconds for it to grey-out the WiFi icon in the menu bar. Then, I would click on it an wait for it to find all networks, including my home network. I then had to select my home network but I did not have to re-enter the network password.
Like others, I did the disk verification and repaired permsissions - it did not resolve the issue. I also deleted the entry in my keychain for my home network's password - that too did not resolve the issue.
Finally, I removed my home network entry from the WiFi Preferred Network list. I then turned off WiFi networks and then turned it back on. When it came back on, I then selected my home network from the list, entered my network password, and checked the Preferred Network checkbox. This resolved my issue - I am able to close my laptop lid, wait a few minutes, and open the lid and my MBA automatically connects to my home network.