It used to be that if I did something that caused two programs to do lots of disk I/O at the same time, OS4 would deadlock. If I ran two large ELFs at the same time it would happen every time.
Well, I ditched SFS for PFS, and the problem went away. I've been running this way for quite some time now, and it hasn't happened once.
At the time I didn't even suspect SFS was the problem. I just switched to PFS because SFS was trashing my data!