I brought a Little Big Disk 1TB Thunderbolt(LBD) and installed 2 128GB SSD(crucial M4 - $106 each) and have my OS on that. I also use the Pegasus R4 for my workflow files. I have tried the SSD's in the pegasus and while fast my boot times were still around 45 seconds. I get 15 seconds with the OS on the SSD's via the Thunderbolt LBD. I didn't go with the LBD SSD stock option because of the speeds. Using my own SSD's in the 1TB LBD got me faster speeds.
LBD 2-128GB SSD is 409/598 write/read
Pegasus R4 4-1TB in raid 0 for 4TB 560/452 write/read
Pegasus R4 2-2TB in raid 0 for 2TB 380/235 write/read
LBD 1TB stock 213/224
LBD SSD stock 333/475