I'm currently using 8.42 with xorg 7.3 (xserver 1.4). the only thing that doesn't work is AIGLX, but I don't use that anyway.
the combinations I tried were:
8.42 + xserver 1.4: 3d, no AIGLX
8.42 + xserver 1.3: 3d + AIGLX (with LIBGL_ALWAYS_INDIRECT set but it was quite slow)
8.41 + xserver 1.4: 3d, needs -ignoreABI
8.41 + xserver 1.3: 3d
My card is a radeon 9550 and distro is slackware-current