ntfs-3g, puffs-ssh and some other filesystems work, but are largely
untested, some fuse filesystems are broken as their support of inode
numbers is to weak (take a look at fuse-sshfs).
There are some issues regarding cache. Original NetBSD puffs code tends
to mmap data to cache it in vm, puffs port doesn't. Besides mmaped pages
can go out of sync.
If you are interested in working on it, do not hesitate contacting me,
I'm interested in finishing the port.
Thanks,
Gleb.