New in Tiger, you can run ls -e from the command line and see the ACL permissions of your files and folders. While I don't have an immediate use for ACLs, I'm sure I will in the future. However, I much prefer the GNU coreutils' ls because of it's colored output. But the GNU ls doesn't seem to support ACLs.
Am I going to be forced to choose between BSD ls and GNU ls? Will GNU ls be supporting ACLs in the future?