I could not download the OS update and have gone to to the Apple Chat window online Wednesday night, May 15, 2013 for help. The problem was not solved despite spending 2 hours with a very nice Apple Chat Tech guy, Nathan Werner. Going over the steps we've gone thru, I eventually mentioned that the wi-fi toggle on/off screen is greyed-out and does not respond. At that point, Nathan said he is sorry and that this problem is a known issue on the apple help site and if the factory reset does not work along with the other trouble shooting steps he's already done, that he can only direct me to the Apple Support group and gave me the 800-676-2775 number. Having set an appointment with the Apple Store already the day before, I did not bother to call the Apple support group any more.
The following day, Thursday, May 16, 2013, I went to the Apple store in Walnut Creek, CA for my appointment. After some brief questions, answers and explanations, Dennis of the Genius Bar told me that the only remedy to the greyed-out wi-fi problem is a Unit Replacement!
I have this phone for more than a year, so warranty has expired and I have to pay$199 if I want a replacement. Since I did not do anything to cause this problem, apparently caused by the new OS update, I do not think that I have to pay for the replacement.
Since a lot of us are having this problem, we should probably band together and ask for free replacement since it is not our fault that they created this problem in the first place!