I'm in the same boat. I performed the update without checking the boards first. Anyway, after software update on my ATV3, I am not able to connect to my home network. Everything was working as advertised before I performed the update an hour ago. I was able to connect via Ethernet, and it works. I am not going to have a Ethernet cable laying across the floor...
Well my issue is fixed, turns out the update with which cause my issue must have locked somthing up in the settings.
I spent some time with one of the support people which is level two or higher and we found that the ATV3 had IP address etc setting for ethernet even with no ethernet/wifi available. We restored the ATV3 several times and even went to earlier versions of firmware to try to undo this, sadly this failed and my ATV had to be replaced, Apple sent out a new one now all is good again.
I suggest you contact them and if you are able to get them to replace it for you.
I did also notice that the iTunes update that came out at the same time had a problem which may have cause this to happen in the first place.
Restore did not work unless you help option key while hitting the Restore.