Nice, hopefully they'll discuss the issues they encountered, and they'll be able to work with the open-source driver developers and also with the hardware vendors and address any problems they find.
I hope they'll find a real solution for the S3TC fiasco too.
In the end, I expect that Valve ports their entire game collection to Linux and that Linux gets top-notch open-source graphics drivers, I also expect the problems with patents (S3TC) to go away.
It would be incredible to see Linux becoming a serious gaming platform and getting better drivers, more market share, etc.
This is what can help Linux if software developers find issues with the Linux kernel and drivers (OSS and proprietary) and share those findings with the community and driver makers (nvidia/AMD) so that viable fixes can be designed and implemented. Another good thing would be developing toolkits to make porting the games to Linux easier and less error prone so that the games will run just as well or even better on Linux as well as Windows.
Props to Valve for undertaking this effort and maybe soon we'll see other game makers taking the Linux plunge.