The "Linux drivers are rubbish" claim boils down to the proprietary ATI Catalyst driver not supporting newer Linux kernels. This though isn't anything new that AMD is always late to the party in supporting new kernel and X.Org releases largely until new releases of Ubuntu (or other officially supported distributions) take advantage of the newer components. Though when it comes to newer kernel support for the Catalyst driver, often times that support can come via third-party patches if the needed change(s) fall within the firegl_public shim code that is distributed as source. For example, right now there are patches available that support up through the Linux 2.6.34 kernel even without official driver support from AMD. With regard to NVIDIA's binary driver supporting new versions of the X.Org Server / Linux Kernel faster, their graphics driver uses less of the existing X.Org/DRI infrastructure used by the open-source drivers with more common code that's shared between their drivers on different platforms, compared to AMD and their Catalyst Linux driver. This ongoing discussion can be found in this thread.
The other discussion that's been particularly interesting with Linux not being ready for Steam already has over 120 comments. This discussion started out as:
I think Valve should wait a year before porting Steam. The multimedia and audio frameworks and APIs on Linux are currently a mess. The APIs and frameworks need to be stablized before any sort of large scale professional game development can begin on Linux.
If Value ports Steam to Linux in its current state, I'm afraid it will become unprofitable and they'll quickly abandon it. If that happened, there would be virtually no professional Linux games for years.
Linux needs to be ready before we fall under the spotlight.
Comments include different opinions and experiences on PulseAudio, GStreamer, ALSA, and SDL. This very heated and lively discussion can be found here. Though having already confirmed Steam and the Source Engine are coming to Linux via our sources, don't expect any delays like this over any Linux audio framework. While the status quo may not be ideal, this hasn't stopped other game companies like id Software from bringing their titles to Linux in the past.
Besides these other two discussions, there are many other active threads within the Phoronix Forums that you can talk about.