WD actually just released terabyte sized Velociraptors, but with the exception of the seek times the 3TB drives are cheaper and faster.
I just saw those recently and was impressed with how cheap they were. I was just hoping for a few used drives to get this done, in BTC hopefully.
I have used every iteration of Raptor/VelociRaptor since their inception and still prefer them over SSDs in sustained READ/WRITE environments...although you can't beat an SSD for it's read times only, if used that way.
Currently I boot my main workstation from a 3 drive RAID 0 SSD array, but my 'working' volume for Video Transcoding etc is still done on a RAID 0 VelociRaptor Array, as the SSDs just get bogged down too fast with multiple read/write requests and the VR's still shine in that respect, regardless of RAID Card.