I have used pfs2 and pfs3 since the 90's.
They run stable and very fast.
The only thing to remember is that is you use a processor specific version that it may not be portable to another system.
Wahoo, what a quick reply! Thanks! 
Thanks for the technical explanation as well.
My aim was to speed up file operations and boot time on the cosy A1200 a bit.
Although your hint about third party FileSystems, I'll give PFS3 a shot and report here for completeness.
If it does have some quirks too, I'll revert back to FFS; but as I'm at it, to the latest version (should be 45.16 AFAIK).
FastFileSystem has served well for the last 2 decades anyway.. 
Amigo1
