SSDs are still quite new technology, that is true, and their reliability compared to hard drives is very hard to determine. It's very hard, though, for me to say that you're going to have less reliability than a mechanical hard drive.
Lately, I've seen a lot of failing mechanical drives, and I don't know if it's just me, but it's above normal. If you're comparing the reliability of an SSD with a mechanical hard drive, then what kind of mechanical hard drive, as the types seem to vary greatly with reliability as well.
For three years I've used two Vertex 120GB SSDs in a RAID 0 array for my operating systems and programs on my primary computer. This system has seen nearly 24/7 up time in those three years, with SEVERAL stress tests, re-installations, everything imaginable perhaps. Finally, just a week ago, one of those Vertex drives began showing errors. The drive would occasionally not be seen in EFI BIOS and when it would, the system would run checkdisk each boot up detecting and fixing numerous errors.
So, three years of continual heavy usage in a strenuous RAID 0 array configuration isn't bad lifespan. That's longer than the Seagate Barracuda 1.5TB hard drives lasted that I used for data. I migrated all that data to new WD 2TB hard drives when I rebuilt the system this spring after the Seagate drives were starting to click and fail. That's longer than a lot of mechanical drives I have seen last lately.
Now, as to your original question though. I believe what you're referring to is the SSD cache system that now can be found in the Intel Z68 chipset, correct? From the reviews I've seen of it, it's a nice feature, but not great yet. The performance benefit is much less than just using a regular SSD as your primary drive but you still have the same cost. In the end, most people recommended using a hybrid drive such as the hybrid SSD/HDD drives Seagate offers.
Now, this is my opinion, but I'm honestly not a proponent of this. If you're wanting to get a SSD it's because of their greatest strength: speed. Don't cut corners if that's your goal. There are other ways of securing your system from a possible faulty or failed drive and still use the speed of the SSD to its full potential that will be less of a complex headache (and not sacrificing your speed) than using a cache system like this or a hybrid drive. Imaged-based backups like others above have mentioned is perhaps the best tool. I've used this myself and it's very effective, requires very little time, and will allow you to use a full SSD without necessarily worrying about it's reliability.
If all you're really wanting to do is speed up the cache or temporary files of your production software, such as Flexi or Photoshop, then maybe what's best is just to add a small SSD in and set the program to point to that drive for its temp files. Better yet, if your system can handle lots of RAM, set up to use a RAMDisk.
