The multiple DAW set-up is no doubt great for recording but recently w/ the power of XITE-1, Gigastudio 4, and other 64 bit apps due out this year, the single / reliable DAW w/ tons of RAM and high speed drives looks very promising indeed.
I already have a couple of SATA RAID cages for recording, O.S. + Apps, and sample content. They were the first cages available from 3Ware and are really efficient for cooling and silencing those fast 10k drives.
Recent designs that were first made by Supermicro in their server cases of yore, are now better designed and available to the general public for very reasonable prices.
The best news is that a SATA II RAID Cage can be equipped to house 5 HDD's, and use SATA I & II.
I have purchased one of these, and a 300GB VelociRaptor after watching my friends' DAW kickin' major ass transferring huge video archives in a RAID 3 Array. I have no need or desire to use RAID in any level, but his configs are always a great place to see and watch new kit in action.
So for a meger 400 USD, I will be able to house all of my old Raptors, plus the new 300GB version w/o changing my memory sub-system, mobo, or CPU.
This new Raptor is a must for high polyphony / streaming sample instruments, or apps.