I don't imagine it is. Anandtech found it wasn't that difficult to evict stuff from the cache you actually wanted. Not to mention that if you start copying anything especially large (your MP3 collection, or installing a couple games from a Steam sale, say) you nuke the cache and are back to mechanical HD performance.
Personally, I prefer to do it manually. Stuff I want to load fast (Windows, applications, games, my profile folder) sit on an SSD. Bulk data sits on a mechanical drive.