File cache is a great way to boost "desktop" performance when you're dealing with tons of small files. I've read in the performance tuning literature that Windows will even store heuristics on clusters of files that are usually opened together so if you access one the others will be prefetched.
Block level cache improves performance in scenarios dealing with giant files - database files, virtual machine hd files, etc. I wouldn't say it's a bad thing although "dumb" may be technically accurate since it's implemented at a level where it's oblivious to files. I don't think file level cache is going to lend much help to mssql or vbox. I wouldn't say that stuff is boring for an end user since I'm an end user and I run mssql and vbox as well as many other applications that maintain very large index files that benefit from block level cache every day.
I usually entrust block level caching of my data to my trusty Areca card with its 4GB ram and BBU however I find the prospect of a software solution very interesting since my CPU is much faster than the onboard ROC and there's much more RAM available. I'd say a sophisticated host-based block-level caching storage filter driver is very welcome here. Me thinks DOS 6.1 just gave Josh a bad rub