I've worked for both TI and the games industry all my professional life. With very limited exceptions I'd say Free Software and video games are not really compatible with each other. In fact, most of the time game companies are allergic to openness out of necessity.
The video game industry is tough and fierce. Much of the competitive advantages of any large studio come directly from the propietary technology they develop for their own games or the engines they license to other studios. Unreal Engine is a very good example of this.
Game companies, from the biggest manufacturer to the smallest studio, are plagued with trade secrets, patents, copyrighted code and tools that can't just be combined easily with their open counterparts. I don't see Valve's culture 'infiltrated' anytime soon because of this.
I think it's great for Linux users to be able to play games without having to boot Windows. But that comes with a compromise: not many advanced users install Ubuntu for their primary computer and I really doubt the software components and drivers needed to run Steam will be well supported in any other distro. Fedora, RHEL and Debian, for instance, have a policy of not including proprietary drivers or patent-encumbered software in the installation disc/image. It may be harder for the users of those distros to make it work.
In conclusion, it's a big win for the Linux user community but not so for the Free Software community.