I have installed last archboot on my macbook air 3,2.
The problem is that if I choose "Arch Linux" in grub legacy menu it trows me to ramfs, but "Arch Linux Fallback" works ok.
This happens on x64 and on x86 if this is of any importance. mkinitcipio doesn't return any erros.
Error: Unable to determine major/minor number of root device '/dev/sda3'"
where sda3 is actually uid of root partition.
I've googled out that this is problem of mkinitcipio: autodetect in hooks.