FreeBSD 7.0
Samba 3.0.32 (and 3.0.28a) from port collection
ZFS (experimental in FreeBSD but stable enough for me)

All is fine while quantity of files (or folders) in any folder is less than about 500 (short English names) or about 200 (long Russian names in UTF8).
When some critical quantity reached, some files "disappears": Samba just doesn't show them.
And some files can be shown twice.
All files are stored normally (console or ftp access shows exactly the same files as copied).
When I copy that files to another folder on ZFS (in console) some "lost" files appears, some visible disappears, diplicates also change.
On UFS all works fine.