FUSE makes it possible to implement a very functional file system
in a normal program rather than requiring a complex addition to
the operating system. More importantly, the FUSE API is very easy
to program for. The large number of interesting and/or useful FUSE
file systems out there is a testament to this. An often-cited
example of such a useful file system is sshfs, which until now was
not available on Mac OS X.
The biggest immediate practical upside is read/write access to NTFS volumes.