Hey.
I just updated my Mid 2012 Retina Macbook Pro this morning to 10.10.2. As many others mentioned, WiFi stopped working on this Mac, but kept working fine on my iPhone 6 Plus and other Macs not running the latest update. Note, I have a Linksys E3200 router running both 2.4 GHz and 5GHz. My Bluetooth was also turned on. I tried the SMC reset twice with no luck.
What did fix the problem was setting a manual IP address to another available IP on the Wi-Fi network. This is done by the following steps:
1. System Preferences -> Network -> WiFi -> Advanced -> TCP/IP
2. Under the first Drop Down Box labeled "Configure IPv4", set it to "Using DHCP with Manual Address".
3. My IPv4 address was set to 192.168.1.107. I changed it to 192.168.1.120 and Wi-Fi started working.
If you are trying this, make sure you know what available IP range is available and which IPs are available. This information is available on your router home page (192.168.1.1). Also, not all IP address are 192.168.1.* it may be be like 10.10.1.1. You will need to confirm this on your router.
Hope this works for you guys.