Michael the kernel panic you faced at the test happened to me quite a few times here but with 3.12 Kernel!
Radeon HD 5850 here and all latest Mesa Xorg git stuff... Using DPM of course...
It happened most of the times when the screen turned off for powersaving or even made the system look stalled! That is not the case for openSuSE's stock 3.11.6 kernel!!
yes it needs GL3.2 so you can set MESA_GLSL_VERSION_OVERRIDE=150 and metro should work but it's ugly, really ugly! We have to wait for GS i think, but i have no hope for my verdeXT
I don't like those portings anyway, the OpenGL version really sucks compared to Direct3D, both in performance and visual quality.
For my standards AAA games are just unplayable in Linux right now, we will have to wait a year or two to reach parity with Windows.
Good to see RadeonSI is on a good pace to getting mature.
By the time of Fedora 21, I could see Metro: LL running it.