I've finished my latest rig rebuild. I went from 2 36GB Raptors in RAID 0 to 2 150GB Raptors in RAID 0. I now have enough space on the resulting drive to install all my games and music - so I left out the 300GB Seagate drive I was using for storage and went from 3 total HD's to 2.
The speed of the drive array actually *feels* remarkably close to what I was used to with the 36GB Raptors. I built a system for a friend the same time I was building mine - his was a single SATA drive and I can again attest that for me there is no way I can go back to a single drive. I'll keep my data backed up on DVD and on external HD's and take my chances on having to do a rebuild.
The only thing I would really like now is to find a utility (Ghost or True Image) that can actually back up my RAID 0 array so that if I do lose a drive I can save some time on the rebuild.