It so happened I upgraded my system from Mavericks to Yosemite today, so this update came right on the heels of that. My system is based on GA-Z68XP-UD3 with UEFI bios, and the only kernel extensions needed have been FakeSMC and NullPowerManagement. (It has wired and wifi cards recognized as native, and uses a Logitech soundbar so doesn't use sound kext.)
The upgrade itself, following the instruction here, went without a hitch (I did reinstall the two kexts). Soon afterwards a notice about OS X update came up from the AppStore, so I let the system take care of it; but this turned out to be a bit clunky experience. After the system was updated it went into a restart; but it then sat idle (shut down but still powered). Manually restarting with a reset button led to the progress bar stopping at about third of the way, then the system hanging with a blank screen without a cursor arrow.
Restarted the system with the Unibeast stick and repaired permission from the command line (quite a few errors here); then downloaded the 10.10.1 update and applied it. After that the system went into a normal restart and it's been fine since.
A bit disappointed that update through the App Store didn't work - it always did under Mavericks.
Use Updater after repairing permissions, reboot and everything went fine except Audio ALC889 show "No devices found" . (Webcam Logitech C525 ok)
Ran Latest Multibeast 7.02 and install kext for ALC889 ... Still No Audio, no devices.
Use old trick found here : Ran MultiBeast version 6.22 , install only ALC889 DSDT Free then Devices and Audio are back fine.
Gigabyte GA-Z68XP-UD4 (F6)