The concept that ZFS uses is truly what Seagate is trying to accomplish. A large array (or just a platter) for actual data storage with a high-grade cache storage in front of that (SSD array, or a small flash cache in Seagate's case). The cache doesn't actually permanantly store data, it just caches the data from it's permanant home on the platters. DIYers have attempted a close approximation of this by having an SSD boot drive, but the problem is this still makes Crysis crap on load times, or perhaps something in your Adobe suite slow, simply because it all got lumped on that "mass storage" drive. What's the solution? How about a proper 32+GB "cache" for the hard drive and a "right-click -> Add folder to flash cache" OS option? The more user-picked cache data, the less space for the "hot data" algorithm, but who would know best that you wanted to load ALL your Crysis map data into the cache? Permanantly. (well until you delete the data or "right-click -> Stop caching". A wimpy sudo-algorithm with a miniscule 4GB of cache isn't going to help much. I'd by a 64GB flash cache + 2TB platter space drive in a heartbeat over a 64GB "boot drive" and a 2TB spindle drive. Especially if it had a "right-click -> Add to cache" option.
/jogs down to the patent office