Tom's Hardware Looks At WinFS
Small object support is good. Robustness against crashes is good if it doesn't cost performance.
A generic "database layer" in the file system, meaning something that allows extensible attributes or something that provides file indexing, is at best superfluous and probably harmful to performance.
If you merely want real-time file indexing, Linux already has the necessary kernel API, and it is independent of file system; all you need for that is change notification (changedfiles, FAM, dnotify) and some user code. The fact that almost nobody bothers running it tells you something.
File systems don't need to get a lot more complicated. Databases are useful, but in addition to file systems, not as a replacement for them.
Linux may well beat Microsoft on this feature, but it's a race that's not worth winning as far as I'm concerned. Please leave the file system alone.