Thanks so much for posting about this drifter29, I have the same issue and no joy from Apple to date.
I have a max-spec mid 2013 Macbook Air, which I also purchased for using as a mac / win machine. It worked perfectly for the first month - using bootcamp for a win 7 machine natively when I need speed or within OSX using Parallels version 8.
My problems with wifi began after Apple pushed out their firmware "fix" for the broadcom 802.11ac wifi (version 6.30.223.74.35 as reported by my machine). Although the wifi continued to work perfectly within OSX, when I ebooted into a win 7 machine it would usually not show any wireless networks. Apple diagnostics (rebooting the Air holding down the "D" key) would likewise give a "No Wi-Fi networks were detected (Reference code CNW007)" error, and the boot up (hold down OPTION key) gray screen would not show any wireless networks either.
I tried many possible solutions in vain - deleting and re-installing the bootcamp from a winclone 4 image (http://twocanoes.com/winclone/ great software BTW), and OSx partition from carbon copy cloner image; reinstalling bootcamp drivers, etc.
Took the device into my local apple repair / reseller, and of course it all worked perfectly in their store. Their AST diagnostics passed 100%, reset SMC etc tried... but the problem recurred at my home (timecapsule wifi) and work (university cisco network). I took photos of the Air at both work and home next to other Idevices all picking up the networks perfectly. I could get around the problem using parallels (which uses the osx wifi and tunnels it into a virtual wired port in windows machine) but speed was slow for graphically intense apps.
I took it into the Apple store in Perth today and the response there was disappointing. Essentially, as it works in OSX, and Bootcamp isn't fully supported by Apple (his words) then it's a microsoft problem. I asked if there is a way to wind back the firmware update (eg: reflash with an older firmware that worked) but I was told that this isn't available. I think that it's disingenouse for Apple to provide Bootcamp as a part of OSX without taking some responsibility for it not working, using drivers that are downloaded form Apple itself.
In despair I returned to work to rant about my woes, but was please so find this thread. I hadn't noticed the double option-key boot trick into windows 7, but it seems to work for me here and I pray that it also works at home tonight. I can also confirm the 15-20 second shutdown spinning waiting circle when rebooting from OS X now as drifter29 reports.
I can live with this double reboot for now so long as it lets me run window reliably, awaiting updated bootcamp drivers from apple. Does Apple / Broadcom / Microsfot know that this is an issue? I'd dowbload and trial some non-bootcamp win 7 drivers for the "Broadcom 802.11ac network adapter; 0117106B&Rev3" but I can't tell whether or not these are available from anywhere other than apple? My driver in windows gives me version 6.30.223.75 currently.
drifter29, please report on your progress with this also, did your wipe & reinstall OSX work?
Cheers again,