I have a NetBSD/i386 3.0 file server at home running Samba 3.x. Read and write access from NetBSD and Windows XP clients is fast (although, under the NetBSD clients, NFS performance wins).

Unfortunately, reading large files from Mac OS X is incredibly slow. Adding the following to /etc/sysctl.conf solves this annoying problem:
This configuration file does not exist in a default installation so simply create it from scratch. rc(8) takes care of it automatically.