The problem with caching that even
@RejZoR should be able to admit and attest to is that if you have any kind of stability issues, caching will not work well and will be corrupted, you will have issues, shit won't work right...and you'll be frustrated beyond belief babysitting a service that should otherwise be left to run and hide in the background. This needs to be mentioned and brought out to the forefront. There is more risk involved with adding extra layers to data handling, but if setup correctly and properly maintained on a stable system, it can really reap some great rewards.
Risk vs. Reward. Spend a little more time checking out the different caching options out there, Intel has it's storage manager SSD caching option, the PrimoCache option is arguably a great one for better control and maintenance. There are other options out there as well. But as always, YMMV. Very much so here.
With SSD's getting more expensive right now...it is sad that 18 months after I bought my Evo850 250GB on sale, I have yet to see it that cheap again...using SSD's as a cache makes sense. 60-120GB, and then buy a decently sized hard drive from 1-4TB+.
I have a 1TB SSD, and I am VERY happy with it as my gaming drive...and I would prefer to just have solid state storage...but also as
@RejZoR pointed out, that shit gets really expensive! Hopefully we can luck out with future fabs to make production cheaper and faster so we can have more drives available at lower costs. Until then we'll have these solutions that let us enjoy some benefits without as much costs, and for things you use a lot and the size of the cache you use, it could really make a nice difference. Again, until something goes wrong.
If I'm going to use an SSD cache, it's going to be an enterprise-grade RAID managed solution, I have found those to be far more stable than standard home-grade solutions, and they should be...but then we're talking $$$$... at that point, might as well just buy a large SSD and be done with it.