Hi rob,
I was hoping our resident mac afficionado would answer your queries first, but... I'm not that mac-savvy save for the fact that I know macs use big-endian byte order.
IMO, if it were me, I'd forego RAID and probably go for WD Raptors if absolute speed is what you want. The downsides are heat, noise, price, and relatively low capacity compared to usual IDE/SATA drives, but those raptors do deliver. - Now if can only get mikep to chime in. -