[calloc]

I used it within OpenSolaris and the real pain is that you have to set up entirely new NFS ACL's that relate to the user writing otherwise files won't be readable from within Solaris as that user, or if it is a shared directory they aren't readable by the outside world and the files are written to disk but no longer visible from the outside world over the network.

[radiowave]

Yes. In general any time you want to access the same file system by multiple different methods, the permissions issue gets rather hairy, but from the point of view of an Apple CIFS server, some well considered finesse in the GUI could be a big help in managing that complexity. In the case of OpenSolaris, it's at least worth mentioning that so long as you do only want to treat a file system as being a share for CIFS clients, it does work just beautifully.

[codex]

Apple's filesystems already support native NTFS ACLs, so I expect that the permissions issues will be no worse than current NTFS/POSIX interop, which is indeed hairy. The best you can do is support the POSIX case very well and the all-ACL case very well.