It works out of the box without boot screen. Flashing 6870 is so easy, it can literally be done in 25 seconds. Netkas tool can dump rom, you convert it to EFI, and flash with zeus.
EDIT: Forgot that the current available firmware is 64bit. no go for MP 1,1. If you wait a few weeks, apple official card will release, hopefully with EBC (32it compatible)
oh, great info, thanks! I was still
under the impression that one would need a pc to flash a "pc version" to mac. just like in the old days when I flashed a 8800GT to use with a Mac