May as well say that about all files on ya drive, ,a quick backup and it becomes irelivent if the machine gets screwed.
as for stability, ffs has never lost a thing since the os35 update and sfs and pfs have hurt alot more people then ffs ever has sicne with ffs there is alot more then just pure luck to getting ya files back.
in my own tests, sfs gets very VERY slow when the partition fills up and becomes quite slow and usless when using lots of small files for say internet file cacheing.
ffs might not be new,updated super speedy or whatever, but its far from bad when setup properly and much more relighable .