To be precise:
It would make a lot of sense to stripe two SSDs to double the speed. Theoretically.
Bare with me.
Second generation SATA interfaces running at 3.0 Gbit/s with a native transfer rate of 3.0 Gbit/s, and taking 8b/10b encoding into account, the maximum uncoded transfer rate is 2.4 Gbit/s (300 MB/s).
Third generation SATA interfaces running at 6.0 Gbit/s with a native transfer rate of 6.0 Gbit/s, and taking 8b/10b encoding into account, the maximum uncoded transfer rate is 4.8 Gbit/s (600 MB/s).
So:
In a computer with two SATA III (6Gbit/sec) interfaces connected to two SATA III SSDs (like the OCZ Vertex 3 MI) you would instead of 550MBytes/sec read 1100MBytes per second.
But (and here comes a big BUT)
Apple has decided to limit the speed on the superdrive bay to SATA II (3Gbit/sec) by connecting to the slower SATA II interface of the chipset (takes less power) instead of the second (existent!!!) SATA III interface !!!!!!
So back in the 2 SSD array but this time in a MBP 15/17 2011 (i5 or i7):
The one in the superdrive bay would read up to 300 MBytes per second, the one in the HDD bay "could" read up to 550MBytes per second so you would say "hey that is a 850MB/sec", right?
Wrong: as the faster has to wait for the slower you read kinda 2x300 so 600 MB/sec.
Wow that is soo much faster then 550 and it costs only double the price of a SSD ;-)
But in a computer with multiple SATA III interfaces it does make a lot of sense (given the need of speed and the cash to go for it).
But dont give up! You will be able to run the 4 SSD raid stripe soon: it will be in a thunderbolt attached enclosure!!! (Although you might be shocked to learn the price... your MBP might even look cheap when compared)
Greetz from Switzerland