STATUS: 
Xorg 1.12: Should be supported around 12-5 or maybe a month later
Xorg 1.11: Supported as of 11-10. 
Xorg 1.10: Working: fglrx 11-4 or newer
Xorg 1.9: Working: fglrx 10-10 or newer. No support for cards older than hd2000
Xorg 1.7: Working: 10-4 or greater. No support for cards older than hd2000
Xorg 1.6: Working: 9-4 or greater, BUT: 9-4 supports only > hd2000 cards.
radeonhd in Xorg >= 1.6 now supports (2d) R7xx cards, and improved support for r4-6xx cards.
Unsupported older cards less than hd2000, use radeon or radeonhd, or do: sgfxi -n
it works out for you.
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Kernels: Working: 3.3 I believe works with latest current.
3.0/3.2; 2.6.39 - use latest driver.
Not doing active testing at this point. As usual, direct install is most reliable.
1: Standard: current-fglrx (current-fglrx / sgfxi): 32 bit: WORKS; 64 bit: WORKS
2: Debian method (debian-fglrx / sgfxi -s): 32 bit: WORKS; 64 bit: WORKS
3: Fglrx latest, fglrx deb builder/installer (sgfxi -D): Erratic.

Always use current driver for newer ATI cards, hd2000 and later.