Ready to stop messing around with slow hard drives and/or want the fastest SSD around?
How about dual eSATA ports as a bonus?
The OWC Mercury Accelsior PCIe SSD is my SSD of choice for my work since it arrived about a year ago—rock solid and I even make a RAID-0 stripe of two of them for about 1100MB/sec of insanely fast disk speed.
The Accelsior is an ideal drive for your Lightroom catalogs, huge working Photoshop files, Photoshop scratch drive and all of the above at the same time. And it works in a Mac Pro (PCIe slot), or any Mac with Thunderbolt (via the OWC Helios enclosure).
I still store my original digital camera image files (NEF, CR2, X3F, ORM etc) on hard drives (capacity issue and not relevant to performance) but all active work, LR catalogs, etc always go onto the Accelsior, so my work is never hindered by disk speed.