Flashing .tar factory image with CWM In the hopes of getting Android 5.0 onto my Nexus 10, I visited Google's factory image download page for the latest image. I noticed however that the file I downloaded was a tar and not a zip. Will this work just the same using CWM to flash it, or do I need to do something special here?
Stock factory images are not supposed to be flashed in recovery. Instead, you should follow the instructions on the page you linked to. Open the tar file, it's probably just a compressed file, just like a zip. 

But first, let me point you to some custom ROMs that ARE flashable in recovery:

Stock

Rastakat

Cyanogenmod 12 (unofficial) 

However, those may all contain extra bugs, as they are made by 3rd party devs.

Now, if you want to install the actual factory images from Google:

First, make sure you have fastboot and adb. If you don't, install the Android SDK.

Extract the files to a folder on your computer, connect your device to a computer and type the commands into a command window (Start -> Command Prompt or type in 

cmd


The commands that you need are the one in green text, but for the sake of completeness:

adb reboot bootloader


If you haven't unlocked the bootloader yet:

fastboot oem unlock


The run the flash-all.bat script:

flash-all.bat 


It should look something like this: