I have tried the amd64-version on a Lenovo R61 as well as on my Macbook. Maybe I should try the i386 on the Macbook because it did not boot properly and I could not use the keyboard.someone already reported this (it's a problem with syslinux), but i have almost no to no hope that this will get fixed; don't have access to macbook hardware.
Unfortunately I don't think this is a bug in syslinux, I have seen it happen with lilo and with windows CDs as well. I belive it is a bug in apples compatibility service module. It seems to be somewhat sensitive to the exact boot method. I haven't tried debian-live but with other CDs I find it usually succeeds if I remove all power from the machine before starting. Then the hold C key during bootup to boot the CD and then release the C key as soon as I hear the CD drive spin up. If I boot through rEFIt it always fails.