It seems that the Arch Linux people found a solution to this problem before Michael:
They should get some of the advertising revenue

For me, a BIOS update actually made things worse on my laptop (HP dv6-3210us, RadeonHD42x0). Now, even with the force flag, I get the dreaded:
[    0.142500] Unable to assume _OSC PCIe control. Disabling ASPM