> you need to support the ability to unlink a file from the file system and keep its data around. Want to run "vim", you need the ability to do renames and hard links

Those seem like pretty basic POSIX filesystem features to be fair. Awkward, sure... there's also awkwardness like symlinks, file locking, sticky bits and so on. But these are just things you have to implement. Are there gotchas that are inherent to FUSE itself rather than FUSE implementations?