SSD cache drive

Having your swap on a second SSD will improve speed if the system isn't already maxed out.

but for the cost at the moment the only real reason you would need this is if you work in digital editing, photoshop, 3d animation or running any software that has it's own swap.

I bought an OCZ SSD to use a cache drive for photoediting with Lightroom. This was a waste of money.   The constant caching of thumbnails eventually worn out the SPEED of the SSD. That is, the SSD still reliably hold data, but the wear-levling algorithm now causes monumental fragmentation of the files. The thumbnail files are constantly getting 'blown' to bits by the SSD wear-leveling: into 10-100's of segments. As such, the files are now (after 6 months) read as fast as from a good HDD. I've finally moved on to using a RAMDISK as a cache drive. Admittedly, the available size is considerably smaller than an SSD, but much, much faster and not prone to permanent fragmentation.  

Correct; there are no performance benefits to be gained by using a SSD to cache a SSD.