For starters DirectX9 is not a problem for Linux and may be a reason DX10 was so quickly and badly developed for Vista (and Vista only at the time).
Proof: Anyone can download the Doom3 demo or the Quake4 demo for Linux (both DX9 games installed with a fairly simple script to "go native"Linux) and compare.
Fact: They run substantially faster than in Windows on identical boxes or the same box, plus the port was/is fairly rudimentary... pre DX10, but then, even DX10 games must maintain DX9 compatibility. Hmmmm....
There are numerous benchmarks, blogs, and shootouts (even at TomsHardware) that have run such comparisons. All the scientific ones agree. Linux is faster and more stable.
So why isn't Linux an important, or even competitive gaming platform?
Opinion: Loki went out of business because of problems with GPL and OpenSource as well as the possible tendency for Linux users to be more hacker-pirate-ish, certainly more familiar with modifying code. So until some large portion of the buying public sees Linux as a viable *for pay* platform, it is unlikely gaming will go much beyond the community level support it has today. That's not altogether bad since getting powerful tools for creating and porting games is very easy in Linux and some game developers cut their teeth on Linux and in fact many modern games are written in Linux. For more info seehttp://en.wikipedia.org/wiki/Game_engine
just for starters.
Maybe you, dear reader, might be the next John Carmack. It is possible. If you read the plain English script and compare to the installation scripts for full games, you may just be the one who ports newer games to Linux, and grows famous, if not rich. Odds aren't presently good but the path is clear and readily available.
While on technicalities, gaming, Linux, and setting the record straight,
I apologize for a previous typo in which I listed LAME as the encoder/decoder for Linux PC game emulators for arcade games. LAME is of course the decoder for mp3s. MAME is what I meant and is the proper arcade device.
Oh and one last shot across the bow of the MBR fiasco. No hard disk, no partition on any hard disk, will stop a thumb drive, CD, or DVD from booting... just to be clear. If your boot CD, etc., Super Grub or otherwise doesn't boot, you have a bad burn or don't know how to setup your boot options in BIOS. Don't blame it on Linux or Grub.