Hi.
I've (kind of) solved this issue, by upgrading all packages relating to graphics to their git versions. So that's mesa, libgl, libdrm, xf86-video-intel, intel-dri, dri2proto.
Now my drivers work (this was indeed a drivers problem) the client doesn't fully work yet, but I tested with walktest, so all errors herein are PS's fault, which pleases me (becasue it's generally easier to fix)