Linux is a pretty terrible OS for gaming. TF2 can break the Ubuntu OS if crashes.
As much as I dislike windows 8, I hate to say it but Linux is just not meant for gaming. It's a whole lot more issues than it's worth, as it will have constant crashes, and can even mess up the OS entirely, thus having to re-install the OS, or go into the files and fix the issue manually if you know what you're doing. Which sadly, most people don't know what they're doing on linux, as it's not a user friendly environment when it comes to gaming, crashes, installs, etc.
This will only make linux worse for the average user, thus being a failure. Not sure why, but I've seen a whole lot of issues with the TF2 on ubuntu 12.04 and definitely 12.10. Issues where the whole system locks up, having you to manually force a reboot, causing the OS to completely destroy it's files, requiring the user to either re-install it, or fix it somehow, usually resulting in the user just uninstalling and using windows.
Sorry valve, but this isn't going to work, linux is not meant for gaming. It's meant for the only thing it's good for - and that's server hosting.