I have an “ultimate” setup— two of my PCIe slots in my 12-core Mac Pro are used for two 960GB Accelsiors (the third slot I need for eSATA).
I boot off a small non-RAID partition (a.Boot), keep a clone as b.Boot, and use the rest of the capacity for a RAID-0 stripe good for well over 1000MB/sec (Scratch).
This is overkill for most people but I am constantly working with huge files, so it is a practical efficiency solution for me. What happens with this setup is (a) I totally forget about disk I/O speed as a factor and (b) the ample capacity means I just get work done without even thinking about it.
Any Mac Pro or any Mac with Thunderbolt (via Helios) can use the Accelsior.
Want your own high performance system for Photoshop or Lightroom? Engage me in consulting before throwing money at the problem (the right choices have to be made).