According to the Sydney Morning Herald, Linus Torvalds reckons that HFS+ is “complete and utter crap”:
"I don't think they're equally flawed - I think Leopard is a much better system," he said. "(But) OS X in some ways is actually worse than Windows to program for. Their file system is complete and utter crap, which is scary."
Macworld UK is mis-reporting this as a pronouncement that Mac OS X itself was “crap and scary”. Great journalism, Macworld.
Anyway, FWIW, I think Linus is wrong. The design of HFS+ is certainly unique, and it does make concurrency difficult on larger SMP configurations (because of its use of a small number of centralised data structures). However, it wasn’t designed for 96-way SMP boxes sat in a server room, and it does what it does quite well, I think. Perhaps he’s referring to the recent tendency to add features by creating files and folders with unusual names, then having the filesystem hide them from the user? It does perhaps seem a little odd, but it is very backwards compatible which is nice.
I also think that he’s wrong that OS X is worse than Windows to program for. I don’t know how much of either Linus has actually done (one supposes he spends most of his time working on Linux), but my experience has been that OS X is very much more pleasant than Windows. And I really don’t know how Linus thinks that the filesystem impacts on that situation at all.