1. You should install Steam for Linux anyway! (Once it's public.)
2. I read games in virtual machines actually work reasonably well these days. (Not with VirtualBox though, sadly.)
(And I will never understand why people love Visual Studio so much. Oh well.)
While that's true, it'll lead to the creation of more games for Linux, particularly with a lot of people apprehensive about the big GUI changes in Windows 8.
More importantly, 90% of my "regular" gaming takes place in Source-based engines (TF2/L4D2), so I would be more than happy as long as those Source games are available on Linux (and I believe that was Valve's plan all along with Steam for Linux).
And Steam has been pretty good at picking up pre-existing Mac ports, notably Civilization IV, Assassin's Creed 2, and several Star Wars games. I think Steam is also largely responsible for the Mac port of Civilization V being a first-class platform instead of the port being outsourced and late (though cross-platform multiplayer support took a while, and so did some of the DLC).
That said Steam on Linux cannot be a bad thing, I think it helped bringing quite a lot of games to OSX as stated elsewhere in this thread. The bad news is that most of the times it means Cider (http://transgaming.com/cider), so the result pale in comparison to rebooting on Windows. I expect the same to happen on Linux: many ports using Wine...
In KVM / Qemu, you need to forward a hardware graphics card to the VM, which means you can't use it in the host OS. It works ok if you have a crossfire or sli setup (since Linux support for either is... lacking) but you still need to have separate displays for the host and guest then.
I haven't tried vmware / xen though.
And while you can do gaming inside a VM with the right combination of hardware and software, it is very tricky to set up.
It's not perfect, but it's mostly pretty good.
Now the real question is, will this steam distribution system handle non X86 chips, and if so will there be limitation on the games selections above and beyond processing ability to run the game. If they can crack that then, I will be truely impressed and see more momentum than you. But it certainly will add momentum, the indirect effect on stabalising and opening up graphics drivers has been one of the greatest side effects of this port of steam onto linux than steam itself.
Be ineteresting how things are a year from now, I smell some roses; But we shall see.
You'll still want to keep a windows computer around if you want to play a wide range of games.
It's the same with steam for mac. Only a handful of games worth playing.
Having a hundred thousand people sign up for his Steam group might be enough to get the ball rolling that way, though.
% wc -l /etc/services
Name Server: NS1.VALVESOFTWARE.COM
Name Server: NS2.VALVESOFTWARE.COM
Name Server: NS3.VALVESOFTWARE.COM
This way they will know in which games people are really interested and I also think that people will gladly support those kickstarter. Overall much less risk on investment.